JP2007507604A - Nanostructured coating systems, components and related manufacturing methods - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating system exhibiting high erosion resistance, corrosion resistance, solid particle impact damage resistance and cavitation resistance at a relatively low temperature.
A substantially ductile and / or corrosion-resistant binder matrix (14) and a plurality of substantially hard nano-sized ceramic particles introduced into the substantially ductile and / or corrosion-resistant binder matrix (14). 12) or nanostructured coating system (10), parts and related manufacturing methods comprising crystal grains. The mean free space distance between the plurality of nano-sized ceramic particles (12) or grains is nanoscale. Optionally, the coating system (10), components, and related manufacturing methods include a plurality of substantially hard micron sized ceramic particles (20) or grains introduced into a substantially ductile and / or corrosion resistant binder matrix (14). May also be included.
[Selection] Figure 1

Description

  The present invention relates generally to nanostructured coating systems, components and related manufacturing methods with improved wear and erosion resistance at high and low temperatures. More specifically, the present invention relates to coating systems, components and related manufacturing methods that utilize a plurality of relatively hard and brittle nano-sized particles introduced in a relatively ductile matrix.

In order to improve the performance of gas turbines, aircraft engines, etc., and to increase their operating efficiency, there is a continuous demand for higher operating temperatures. However, as the operating temperature increases, it is necessary to increase the high temperature durability of parts such as gas turbines and aircraft engines. With the composition and development of nickel-base, cobalt-base and iron-base superalloys, the high-temperature performance has been greatly improved. Such superalloys are designed to withstand temperatures above about 800 ° C. However, when used in the manufacture of parts such as gas turbines and aircraft engines, these superalloys are susceptible to damage from oxidation and hot corrosive action and cannot retain the proper mechanical properties. For this reason, such parts are protected by the environment or a thermal barrier coating (commonly referred to as “thermal barrier coating”).

  High temperature wear resistance, erosion resistance, abrasion resistance and strength are important properties for components and coating systems such as gas turbines, aircraft engines. To ensure adequate wear resistance, erosion resistance, abrasion resistance and strength at high temperatures, the coating system must retain its hardness, be reasonably tough and oxidation resistant. The useful operating range of conventional high temperature coating systems such as carbides, triballoys is limited to about 800 to about 850 ° C. Similarly, pure single phase ceramic coating systems have relatively low toughness and do not function well at high temperatures. Currently available coating systems with the best wear resistance, erosion resistance, abrasion resistance and strength at high temperatures (above about 1000 ° C.) include L605 bulk material and yttria stabilized zirconia (YSZ). The MCrAlY-alumina micron-scale coating system containing a plurality of relatively hard and brittle micron-sized ceramic particles shows properties comparable to the WC-Co coating system in room temperature wear and erosion tests, but still performs well at high temperatures. Does not work.

  Thus, there remains a need for coating systems that provide high wear resistance, erosion resistance, wear resistance and strength at high temperatures (above about 1000 ° C.). This coating system must retain its hardness, be reasonably tough and oxidation resistant.

  Similarly, hydropower turbine components and the like are subject to significant erosion at relatively low temperatures when exposed to, for example, silt in rivers above about 1000 ppm. This problem can be a particularly serious problem in South and Southeast Asia and South America where silt content in the rainy season can exceed about 50,000 ppm. The resulting erosion damage reduces operating efficiency and can require costly maintenance-related shutdowns and heavy parts replacement every few years. In order to avoid such problems, many power plants stop the operation of the hydropower turbine when the silt content reaches a predetermined limit, for example about 5000 ppm.

  These problems have been addressed by manufacturing hydropower turbine parts from 13-4 martensitic stainless steel, 16-5-1 stainless steel, etc. to mitigate corrosion and improve erosion resistance of the parts. Yes. Ceramic coating systems such as alumina, alumina-titania and chromia applied by atmospheric plasma spraying have also been used with limited success. Similarly, NiCrBSi + WC-CoCr coating systems having micron-sized WC grains applied by thermal spraying and melting processes and WC-CoCr coating systems having micron-sized WC grains implemented by the hybrid DJ HVOF method are also utilized. Yes. However, none of these coating systems exhibit adequate erosion resistance under conditions where the sedimentation and mud content is high and the water speed is about 30 to about 70 m / s.

Thus, there remains a need for coating systems that exhibit high erosion resistance, corrosion resistance, solid particle impact damage resistance and cavitation resistance at relatively low temperatures.
US Pat. No. 5,242,363

In various embodiments, the present invention provides nanostructured coating systems, components and related manufacturing methods that exhibit improved wear resistance, erosion resistance, abrasion resistance and strength at elevated temperatures (greater than about 1000 ° C.). . The coating system includes a plurality of relatively hard and brittle nano-sized ceramic particles introduced into a relatively ductile oxidation resistant matrix. Although the oxidation resistant matrix acts as a binder, mention may be made of metal alloy matrices with proven high temperature performance. For example, as a metal alloy matrix, a nickel base alloy (eg, Ni base superalloy, NiCr, NiCrAlY, etc.), a cobalt base alloy (eg, L605, HS188, CoCrAlY, etc.), an intermetallic compound system (eg, NiAl, Ni ₃ Al) Or a shape memory alloy that absorbs impact energy through martensitic transformation. Nano-sized ceramic particles include aluminum oxide, zirconium oxide, yttrium oxide, yttrium-based garnet, mullite, hafnia, or a suitable combination thereof. Detrimental interactions between the metal alloy matrix and the nano-sized ceramic particles are avoided by selecting a metal / oxide combination that is unlikely to cause a runaway reaction. Preferably, the volume fraction of the ceramic phase is about 10 to about 95%, the particle size of the nano-sized ceramic particles is about 5 to about 200 nm, and the mean free space distance is about 200 nm or less, more preferably about 100 nm or less. Optionally, in the bimodal embodiment of the present invention, a plurality of relatively hard brittle micron sized ceramic particles may be introduced into the metal alloy matrix.

  The coating system of the present invention not only has increased hardness at high temperatures, but also has increased resistance to crack nucleation and propagation. Specifically, relatively hard and brittle nano-sized ceramic particles act as an obstacle to dislocation motion, thereby giving increased hardness at high temperatures and suppressing deformation of the metal alloy matrix. Cracks are relatively hard and brittle ceramic particles are nano-sized (or nano- and micron-sized), so nucleation does not occur easily, and complex modified microstructures meander the propagation path and propagation is also unlikely.

  In various embodiments, the present invention provides nanostructured coating systems, components and related manufacturing methods that exhibit improved erosion resistance, corrosion resistance, solid particle impact damage resistance and cavitation resistance at relatively low temperatures. Coating systems also include those in which a plurality of nano- and micron-sized WC crystal grains are introduced in a corrosion-resistant CoCr binder. By using nano-sized WC crystal grains, the occurrence of fine cracks in the WC crystal grains is reliably avoided, and the average distance between the WC crystal grains is surely reduced, thereby improving the erosion resistance of the coating system. The use of micron-sized WC grains improves the erosion resistance of the coating system at relatively shallow angles and makes the propagation path in the CoCr binder meander. By using nano-sized WC crystal grains having a relatively small mean free distance, the toughness of the entire coating system is improved and the CoCr content can be reduced.

  The coating system of the present invention comprises thermal spraying, composite plating (electrical or electroless), brush composite plating, electron beam-physical vapor deposition, thermal spray molding, mechanical alloying and subsequent powder compression, mixing with brazing alloys. It is applied to parts by brazing process, thermal spraying and melting, laser remelting, and other conventional processes.

  In one embodiment of the present invention, the high temperature coating system includes a substantially ductile binder matrix and a plurality of substantially hard nano-sized ceramic particles introduced into the substantially ductile binder matrix. The mean free space distance between the nano-sized ceramic particles is nanoscale.

  In another embodiment of the invention, the high temperature component is introduced into a substrate having a surface, a substantially ductile binder matrix disposed adjacent to the surface of the substrate, and a substantially ductile binder matrix. A plurality of substantially hard nano-sized ceramic particles, and the mean free space distance between the plurality of nano-sized ceramic particles is nanoscale.

  In yet another embodiment of the present invention, a method of manufacturing a high temperature coating system comprises providing a substantially ductile binder matrix and placing a plurality of substantially hard nano-sized ceramic particles in the substantially ductile binder matrix. The mean free space distance between the plurality of nano-sized ceramic particles is nanoscale.

  In yet another embodiment of the invention, the low temperature coating system includes a substantially corrosion resistant binder matrix, wherein the substantially corrosion resistant binder matrix is one or more of cobalt, chromium, nickel, stainless steel, stainless steel. And alloys of cobalt, iron-base alloys, amorphous materials and shape memory alloys. The low temperature coating system also includes a plurality of substantially hard nano-sized grains in a substantially corrosion-resistant binder matrix, wherein the plurality of substantially hard nano-sized grains are one or more types of tungsten carbide. , Titanium carbide, titanium diboride, titanium alloy nitride, boron carbide, cubic boron nitride, silicon carbide, silicon nitride, diamond and oxides, and between multiple substantially hard nano-grain grains The mean free distance is nanoscale.

  In yet another embodiment of the present invention, the low temperature component includes a substrate having a surface and a substantially corrosion resistant binder matrix disposed adjacent to the surface of the substrate, and is substantially corrosion resistant. Examples of the binder matrix include one or more kinds of cobalt, chromium, nickel, stainless steel, stainless steel alloyed with cobalt, iron-based alloy, amorphous material, and shape memory alloy. The low temperature component also includes a plurality of substantially hard nano-sized grains introduced into a substantially corrosion-resistant binder matrix, wherein the plurality of substantially hard nano-sized grains are one or more carbonized. Tungsten, titanium carbide, titanium diboride, titanium alloy nitride, boron carbide, cubic boron nitride, silicon carbide, silicon nitride, diamond and oxide, plus a plurality of substantially hard nano-sized grains The mean free distance between is nanoscale.

  In yet another embodiment of the present invention, a method for producing a low temperature coating system includes providing a substantially corrosion resistant binder matrix, wherein the substantially corrosion resistant binder matrix is one or more of cobalt, chromium, Includes nickel, stainless steel, stainless steel alloyed with cobalt, iron-based alloys, amorphous materials and shape memory alloys. The method also includes introducing a plurality of substantially hard nano-sized grains into a substantially corrosion-resistant binder matrix, wherein the plurality of substantially hard nano-sized grains are one or more. Tungsten carbide, titanium carbide, titanium diboride, titanium alloy nitride, boron carbide, cubic boron nitride, silicon carbide, silicon nitride, diamond and oxide, and a plurality of substantially hard nano-sized particles The mean free distance between grains is nanoscale.

  As described above, in various embodiments, the present invention provides nanostructured coating systems, components and related manufacturing that exhibit improved wear resistance, erosion resistance, abrasion resistance and strength at elevated temperatures (greater than about 1000 ° C.). Provide a method. These nanostructured coating systems, components and related manufacturing methods exhibit the improved properties described above because they retain their hardness, are relatively tough, and are oxidation resistant. In various embodiments, the present invention also provides nanostructured coating systems, components and related manufacturing methods that exhibit improved erosion resistance, corrosion resistance, solid particle impact damage resistance and cavitation resistance at relatively low temperatures.

Referring to FIG. 1, the high temperature coating system 10 of the present invention comprises a plurality of relatively hard brittle nano-sized ceramic particles 12 introduced in a relatively ductile oxidation resistant matrix 14. As used herein, “relatively” or “substantially” hard means about 20% or more harder than quartz (greater than about 1200 Hv), and “relatively” or “substantially” ductile means WC It means having a ductility lower than that of Co. Although the oxidation resistant matrix 14 acts as a binder, mention may be made of metal alloy matrices that have proven high temperature performance. For example, as a metal alloy matrix, a nickel base alloy (eg, Ni base superalloy, NiCr, NiCrAlY, etc.), a cobalt base alloy (eg, L605, HS188, CoCrAlY, etc.), an intermetallic compound system (eg, NiAl, Ni ₃ Al) Etc.), or shape memory alloys that absorb impact energy through martensitic transformation. In general, binder materials include, for example, metals, alloys, superalloys, brazing alloys, multiphase alloys, low temperature alloys, high temperature alloys (designed for use at temperatures above about 700 ° C.), intermetallic compounds. , Semiconductor metals, or ceramic materials. Examples of the superalloy include a nickel base superalloy, a cobalt base superalloy, and an iron base superalloy. Brazing alloys include nickel or cobalt alloys and chromium, tungsten, boron or silicon. Multiphase alloys include those of the formula MCrAlY, where M is nickel, cobalt, iron or a suitable combination thereof. Suitable examples include, but are not limited to, NiCrAlY, CoNiCrAlY, CoCrAlY, and FeCrAlY, with a Cr content of about 20 to about 35%, an Al content of about 8 to about 12%, and a Y content of about 2%. And the balance is Ni, Co and / or Fe. Examples of the low temperature alloy include austenitic stainless steel, ferritic stainless steel, aluminum base alloy, cobalt base alloy, and titanium base alloy. Examples of the intermetallic compound include nickel aluminide, trinickel aluminide, titanium aluminide, trititanium aluminide, five niobium trisilicide, niobium disilicide, and triniobium silicide. An example of the semiconductor metal is silicon. An example of the ceramic material is a ductile ceramic oxide such as titanium dioxide. Optionally, the binder material may contain a trace amount of a wetting agent such as titanium, magnesium, oxygen, iron, nickel, chromium and the like. Preferably, the binder remains stable in the temperature range of about 500 to about 1150 ° C.

  The nano-sized ceramic particles 12 may take the form of a plurality of nanoparticles, nanofibers, nanotubes, nanotetrapods, and the like. Nano-sized ceramic particles 12 include aluminum oxide, zirconium oxide, yttrium oxide, yttrium-based garnet, mullite, hafnia, or a suitable combination thereof. In general, the nano-sized ceramic particles 12 include ceramic oxide, ceramic carbide, ceramic nitride, ceramic boride, metal silicide, ceramic oxycarbide, ceramic oxynitride, carbon (eg, diamond), and the like. Examples of the ceramic oxide include a metal oxide, a semiconductor oxide, and a mixed oxide. Examples of the metal oxide include rare earth metal oxides, refractory metal oxides, refractory oxides, and reactive metal oxides. Examples of the semiconductor oxide include silicon oxide. Examples of mixed oxides include yttrium aluminum oxide, yttrium iron oxide, zirconium silicate, calcia stabilized zirconia, ceria stabilized zirconia, magnesia stabilized zirconia, yttria stabilized zirconia, mullite, garnet, and metal titanate. , Metal lanthanates, metal zirconates or metal silicates. The metal of the metal titanate, metal lanthanate, metal zirconate or metal silicate includes aluminum, magnesium or zirconium. Examples of rare earth metal oxides include oxides containing lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium or yttrium. Examples of the refractory metal oxide include oxides containing zirconium, hafnium, chromium, molybdenum, niobium, rhenium, tantalum, tungsten, or vanadium. Examples of the refractory oxide include oxides containing aluminum, magnesium, or calcium. Examples of reactive metal oxides include oxides containing titanium, nickel, cobalt, or iron. Examples of the ceramic carbide include metal carbide and semiconductor carbide. Examples of the metal carbide include carbide containing chromium, niobium, hafnium, tantalum, titanium, molybdenum, boron, or tungsten. As the semiconductor carbide, for example, there is a carbide containing silicon. Examples of ceramic nitride include nitride containing aluminum, chromium, niobium, silicon, boron, zirconium, or titanium. Examples of ceramic borides include borides containing titanium diboride or zirconium diboride. Examples of the metal silicide include a silicide containing chromium, molybdenum, tantalum, titanium, tungsten, or zirconium. Further, as the nano-sized ceramic particles 12, as described in more detail below, a commercially available tungsten carbide material can be modified by adding chromium to improve erosion resistance.

  The relatively hard and brittle nano-sized ceramic particles 12 can be made relatively ductile using a milling device such as, for example, a mechanical alloying device, a high energy ball milling device, a reactive ball milling device or a cryogenic milling device. Is introduced into the oxidation resistant matrix 14. In general, the binder powder and ceramic particles are uniformly blended to form a particulate material that is sprayed or brazed. Alternatively, ceramic particles are suspended in a plating bath and electrolytically trapped to form a composite coating by a tank or brush plating process. Alternatively, the ceramic particles may be suspended in an electroless plating bath and trapped to form a composite coating. Finally, as described above, the binder powder and ceramic particles may be compressed together to form one or more composite ingots and deposited in an electron beam physical vapor deposition process to form nanoparticles in the binder matrix. .

  Detrimental interactions between the metal alloy matrix and the nano-sized ceramic particles 12 are avoided by selecting metal-oxide combinations that are less prone to runaway reactions. The metal-oxide combination is also selected to be immiscible with the metal alloy matrix. Unlike carbides and nitrides, carefully selected metal-oxide combinations are more thermodynamically stable than the corresponding metal alloys, do not dissolve in the metal alloy matrix, and retain the ductility of the metal alloy matrix. .

Important microstructure factors in obtaining improved wear resistance, erosion resistance, and abrasion resistance at high temperatures include volume fraction of ceramic phase, grain size of ceramic particles and mean free distance of metal alloy matrix There is. Specifically, wear resistance is a function of hardness (H) and fracture toughness (K _c ). Hardness is a function of average free space distance between ceramic particles (λ ^−1/2 ), and fracture toughness is a function of crystal grain size of ceramic particles and average free space distance between ceramic particles (d / λ). . The relationship between d / λ and fracture toughness for both the nano and micron regions is shown in FIG. As the grain size (d) of the ceramic particles decreases, the stress concentration associated with the ceramic particles embedded in the metal alloy matrix decreases and the compatibility with the tough and ductile matrix increases. Preferably, the metal alloy matrix does not include an embrittled dissolved phase.

  Referring again to FIG. 1, the volume fraction of the ceramic phase is preferably about 10 to about 95%, and the particle size or particle size 16 of the nano-sized ceramic particles 12 is about 5 to about 250 nm. As a result, the average free space distance 18 between the dispersed nano-sized ceramic particles 12 is about 200 nm or less, preferably about 100 nm or less. The high temperature hardness of the coating system 10 obtained in this way is ensured. Adequate toughness is ensured by the nanoscale of the relatively hard, brittle, nanosized ceramic particles 12, while maintaining the inherent ductility of the metal alloy matrix while limiting the initial defect size to the nanoscale.

  To obtain improved oxidation resistance above about 1000 ° C. with the coating system 10 of the present invention, the metal alloy matrix is selected from MCrAlY, L605, HS188, aluminide (Ni or Ti), and the like. At intermediate temperatures (less than about 850 ° C.), the metal alloy matrix is selected from Trivalloy 800, NiCrBSi, Ni20% Cr5% Al, Ni20% Cr, and the like. However, it will be apparent to those skilled in the art that other suitable materials can be used.

  The coating system 10 exhibits both high hardness and high toughness, ensuring improved wear resistance. Since the dispersed nano-sized ceramic particles 12 have a relatively low chemical affinity for the metal facing surface, the coating system 10 also exhibits improved wear resistance. This is observed under high pressure contact conditions, particularly when using a suitable Co-based metal alloy matrix such as Trivalloy or L605. The nanoscale of the nano-sized ceramic particles 12 has a scoring due to the relatively hard brittle nano-sized ceramic particles 12 entering the facing material when high pressure contact with the facing material occurs. Do not wake up. Thus, the nanoscale of the nanosized ceramic particles 12 minimizes counter-surface wear.

  Under erosion conditions, a coating system containing mainly hard brittle components can behave as ductile if the microstructure grain size of the hard brittle components is substantially smaller than the associated impact depression. . However, the ductile response is greatly limited by the presence of hard brittle components. The erosion rate under such conditions decreases with a decrease in the mean free space distance between the hard brittle components. Improved erosion resistance is obtained due to the nano-sized ceramic particles 12 and the nanoscale of mean free space distance 18 of the present invention.

  Referring to FIGS. 3 and 4, in the bimodal embodiment of the present invention, a plurality of relatively hard brittle micron-sized ceramic particles 20 are also introduced into the metal alloy matrix to provide relatively high and relatively low temperatures. Improved wear resistance, erosion resistance, wear resistance and strength can be obtained. The bimodal coating system 30 includes a brittle mode 32 that exhibits only moderate wear at high temperatures and a ductile mode 34 that exhibits only low wear at high temperatures. Preferably, the micron-sized ceramic particles 20 have a particle size or particle size not exceeding about 1 micron. With respect to the brittle mode 32, cracks present in the relatively hard brittle micron-sized ceramic particles 20 are blunted by the relatively ductile metal alloy matrix. As described above, with respect to the ductile mode 34, cracks in the relatively hard brittle nano-sized ceramic particles 12 are prevented and the ductile deformation of the metal alloy matrix is severely constrained, resulting in improved wear resistance. Specifically, the nano-sized ceramic particles 12 act as an obstacle to dislocation motion, thereby giving increased hardness at high temperatures and suppressing deformation of the metal alloy matrix. Cracks are less prone to nucleation because the brittle ceramic particles are nano-sized, and are less prone to propagation because complex modified microstructures meander the propagation path.

  Micron-sized ceramic particles 20 include aluminum oxide, zirconium oxide, yttrium oxide, yttrium-based garnet, mullite, hafnia, or a suitable combination thereof. Generally, the ceramic particles 20 having a micron size include ceramic oxide, ceramic carbide, ceramic nitride, ceramic boride, metal silicide, ceramic oxycarbide, ceramic oxynitride, carbon (for example, diamond), and the like. Examples of the ceramic oxide include a metal oxide, a semiconductor oxide, and a mixed oxide. Examples of the metal oxide include rare earth metal oxides, refractory metal oxides, refractory oxides, and reactive metal oxides. Examples of the semiconductor oxide include silicon oxide. Examples of mixed oxides include yttrium aluminum oxide, yttrium iron oxide, zirconium silicate, calcia stabilized zirconia, ceria stabilized zirconia, magnesia stabilized zirconia, yttria stabilized zirconia, mullite, garnet, and metal titanate. , Metal lanthanates, metal zirconates or metal silicates. The metal of the metal titanate, metal lanthanate, metal zirconate or metal silicate includes aluminum, magnesium or zirconium. Examples of rare earth metal oxides include oxides containing lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium or yttrium. Examples of the refractory metal oxide include oxides containing zirconium, hafnium, chromium, molybdenum, niobium, rhenium, tantalum, tungsten, or vanadium. Examples of the refractory oxide include oxides containing aluminum, magnesium, or calcium. Examples of reactive metal oxides include oxides containing titanium, nickel, cobalt, or iron. Examples of the ceramic carbide include metal carbide and semiconductor carbide. Examples of the metal carbide include carbide containing chromium, niobium, hafnium, tantalum, titanium, molybdenum, boron, or tungsten. As the semiconductor carbide, for example, there is a carbide containing silicon. Examples of ceramic nitride include nitride containing aluminum, chromium, niobium, silicon, boron, zirconium, or titanium. Examples of ceramic borides include borides containing titanium diboride or zirconium diboride. Examples of the metal silicide include a silicide containing chromium, molybdenum, tantalum, titanium, tungsten, or zirconium.

  The nanostructured coating system 10, 30 of the present invention can be sprayed, composite plating (electrical or electroless), brush composite plating, electron beam physical vapor deposition, thermal spray molding, mechanical alloying and subsequent powder compression, brazing. It is applied to a component made of a base material by means of mixing with an alloy and a brazing process, spraying and melting, laser remelting and other conventional processes. Where very thick coatings are required, the metal-oxide combination of the present invention is provided by thermal spraying and melting processes and subsequent melting by reheating the metal alloy matrix. The coating system of the present invention can also be synthesized to a grade that can be sprayed by agglomeration and sintering or mechanical alloying followed by agglomeration to the desired particle size. Adjust the partial pressure of oxygen during powder synthesis to increase the metal-oxide adhesion. Suitable thermal spray equipment / methods include HVOF and HVAF methods, wire arc methods, atmospheric plasma methods, low pressure plasma methods, and the like.

  Engineering components that utilize the nanostructured coating systems 10, 30 of the present invention include those that come with gas turbines, hydropower turbines, aircraft engines, internal combustion engine engines, and the like. For example, engineering parts include guide vanes, surface materials, needle valves or valve seats, shafts, bearing seals, compressor blades, seals, runners, centrifugal pump impeller blades, centrifugal compressor impeller blades, intermediate seals, piston rods Seals, piston rings, fan blades, compressors, wear resistant tips for steam turbines, wear resistant tips for gas turbines, labyrinth seals, gas flow path seals for discs, exhaust valves for internal combustion engines, brush seals, internal combustion engine engines Turbocharged impeller, internal combustion engine connecting rod, intermediate lip seal, moving parts of combustor assembly, HPT post-stage blade coating, LPT blade coating, z-notch interlock, afterburner support, exhaust flap, cutting tool Etc., and the like.

  Referring to FIG. 5, for a relatively low temperature hydropower turbine, a sprayed tungsten carbide coating system is used to protect the parts from wear, erosion and wear. However, such damage is typically caused by a combination of solid particle erosion, corrosion, solid particle impact damage and cavitation. Often, chromium is added to a cobalt binder containing a plurality of micron-scale WC grains to resist the overall effects of erosion and corrosion. However, the low temperature nanostructured coating system 40 of the present invention maintains their corrosion resistance while improving the erosion resistance and toughness associated with these conventional low temperature coating systems.

As described above, the low temperature nanostructured coating system 40 of the present invention includes a plurality of nano-sized WC crystal grains 42 and optionally micron-sized WC crystal grains 44 introduced into a corrosion-resistant CoCr binder or matrix 46. By using nano-sized WC crystal grains 42, the occurrence of fine cracks in the WC crystal grains is reliably avoided, the average distance 48 between the WC crystal grains is reliably reduced, and the erosion resistance of the coating system 40 is improved. . The use of micron-sized WC grains 44 improves the erosion resistance of the coating system 40 at relatively shallow angles and causes the propagation path in the CoCr binder 46 to snake. The use of nano-sized WC grains 42 having a relatively small mean free distance 48 improves the overall toughness of the coating system 40 and can reduce the CoCr content. Also, the use of nano-sized WC grains 42 with a relatively small mean free distance 48 improves the toughness of the CoCr binder 46 in situations where the CoCr binder 46 includes a dissolved phase that reduces the ductility of the CoCr binder 46. Alternatively, the CoCr binder 46 may be nickel, stainless steel, stainless steel alloyed with cobalt, iron-based alloys, amorphous materials and / or other shape memory alloys such as shape memory alloys that absorb impact energy through martensitic transformation. It can be replaced with a metal component. Similarly, nano-sized WC grains 42 may be made of titanium carbide, titanium diboride, titanium alloy nitride, boron carbide, cubic boron nitride, silicon carbide, silicon nitride, diamond, Al ₂ O ₃ or the like. An oxide may be substituted. These alternative particles need only be harder and / or tougher than WC and may be light. Other possible combinations include matrix alloys having nanoparticles deposited from bulk matrix alloy materials such as gamma prime or carbide. Optionally, these nanoparticles are precipitated from materials such as amorphous alloy starting materials during the high temperature coating process. Amorphous materials provide a strong matrix material due to the absence of dislocations and grain boundaries, and can be used to produce fine nano-sized grains for dislocation collapse and improved strength.

  Typical CoCr content of commercial WC-CoCr spray powder is about 10 wt% Co and about 4 wt% Cr. The CoCr content of the coating system 40 of the present invention is from about 6 wt% (about 4 wt% Co and about 2 wt% Cr) to about 14 wt% (about 5 wt% Cr or less, the balance being about 9 wt% Co or less). Typically, coating systems with a low metal binder content have excellent erosion resistance at relatively shallow impact angles, but are relatively brittle, exhibit poor erosion resistance at relatively steep impact angles, and inferior fracture Showing toughness. The use of nano-sized WC grains 42 and a low CoCr content reduces the mean free distance between WC grains, increases the inherent toughness of the coating system 40 and improves its erosion resistance. Preferably, the nano-sized WC grains 42 have a particle size or particle size 50 of about 10 to about 250 nm.

  Optionally, the use of micron-sized WC grains 44, preferably having a particle size or particle size of about 0.5 to about 2 microns, allows the coating system 40 to withstand erosion at relatively shallow impact angles, and CoCr Even if a microcrack is formed in the binder 46, the crack must propagate around the WC crystal grain 44 having a micron grain size, and therefore its propagation meanders. Preferably, the average distance 48 between WC grains is about 50 to about 500 nm, more preferably about 50 to about 250 nm. Preferably, the total volume fraction of WC grains is about 5 to about 95%, more preferably about 50 to about 95% (about 70% of the total volume fraction comprises nano-sized WC grains 42, About 30% of the percentage includes WC grains 44 of micron size). When using stainless steel alloyed with nickel, stainless steel and / or cobalt, their total volume percentage is preferably less than about 20%.

  Cr in the CoCr binder 46 plays two important roles. First, Cr improves the overall corrosion resistance of the coating system 40. Next, Cr limits the dissolution of the primary WC during the thermal spraying process, ensures a high retention of the primary WC phase, and improves the erosion resistance of the coating system 40.

  The low temperature nanostructured coating system 40 of the present invention is applied to a component made of a substrate using either a conventional thermal spray process, preferably an HVOF or HVAF process, or a cold spray process. Examples of the substrate include Mg, Al, Cu, Fe, Ni, or Co-based alloys. The key requirements associated with the thermal spray process are to optimize the thermal spray conditions to limit WC dissolution during this process, ensure proper retention of the WC phase, and reduce the formation of the eta (η) phase in the binder It is to become. The coating system 40 can also be applied to parts by mixing WC-CoCr powder with a brazing alloy matrix and brazing the blend to the surface by a brazing tape process or slurry coating and firing. The WC-CoCr powder is blended with a composition such as NiCrBSi and deposited with a combustion spray torch and then melted or blended with a low melting flux or other brazing alloy and melted using a laser or the like. The ratio of braze alloy to WC-CoCr powder is optimized to ensure that the blend exhibits adequate erosion resistance.

  Although the present invention has been illustrated and described with reference to preferred embodiments and examples thereof, it will be apparent to those skilled in the art that other embodiments and examples may perform similar functions and / or achieve similar results. it can. All such equivalent embodiments and specific examples belong to the technical idea and technical scope of the present invention, and are encompassed by the claims.

FIG. 1 is a conceptual illustration of one embodiment of a nanostructured coating system of the present invention comprising a plurality of relatively hard brittle nano-sized ceramic particles introduced into a relatively ductile oxidation resistant matrix. . FIG. 2 shows the grain size of the ceramic particles in the cermet coating system and the mean freedom between the ceramic particles for both the nano and micron regions in a system in which the binder is ductile and does not contain a dissolved hard phase. 4 is a graph illustrating the conceptual relationship between the spatial distance (d / λ) and the fracture toughness (K _c ) of the cermet coating system. FIG. 3 illustrates a nanostructured structure of the present invention comprising a plurality of relatively hard brittle nano-sized ceramic particles and a plurality of relatively hard brittle micron-sized ceramic particles introduced in a relatively ductile oxidation resistant matrix. It is a conceptual explanatory drawing of another embodiment of a coating system. FIG. 4 is a conceptual explanatory diagram highlighting the brittle and ductile modes of the bimodal nanostructured coating system of FIG. FIG. 5 is a conceptual illustration of another embodiment of the nanostructured coating system of the present invention comprising a plurality of nano-sized ceramic grains and a plurality of micron-sized ceramic grains introduced in a corrosion resistant metal binder. .

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 High temperature coating system 12 Relatively hard brittle nano-sized ceramic particles 14 Relatively ductile oxidation resistant matrix 18 Average free space distance between nano-sized ceramic particles 12 20 Relatively hard brittle micron-sized ceramic particles

Claims (14)

A substantially ductile binder matrix (14);
A plurality of substantially hard nano-sized ceramic particles (12) introduced into a substantially ductile binder matrix (14), and between the plurality of substantially hard nano-sized ceramic particles (12). High temperature coating system (10) with a mean free space distance of nanoscale. The coating system of any preceding claim, wherein each of the plurality of nano-sized ceramic particles (12) has a particle size of about 5 to about 200 nm. The coating system of claim 1, wherein the mean free space distance between the plurality of nano-sized ceramic particles (12) is less than about 200 nm. The coating system of claim 3, wherein the mean free space distance between the plurality of nano-sized ceramic particles (12) is less than about 100 nm. The coating system of claim 1, wherein the volume fraction of the plurality of nano-sized ceramic particles (12) is from about 10 to about 95%. The coating system of claim 1, wherein the plurality of nano-sized ceramic particles (12) comprises a plurality of particles selected from the group consisting of nanoparticles, nanofibers, nanotubes, nanotetrapods, and combinations thereof. The plurality of nano-sized ceramic particles (12) comprises one or more ceramic oxides, ceramic carbides, ceramic nitrides, ceramic borides, metal silicides, ceramic oxycarbides, ceramic oxynitrides or carbons. The coating system according to 1. The binder matrix (14) comprises one or more metals, alloys, superalloys, brazing alloys, multiphase alloys, low temperature alloys, high temperature alloys, intermetallic compounds, semiconductor metals, ceramic materials or shape memory alloys. The coating system according to 1. The coating system according to claim 1, wherein the binder matrix (14) comprises a wetting agent. The coating system of claim 1, further comprising a plurality of substantially hard micron sized ceramic particles (20) introduced into a substantially ductile binder matrix (14). The coating system of claim 10, wherein each of the plurality of micron-sized ceramic particles (20) has a particle size of about 1 micron or less. The coating system of claim 10, wherein the volume fraction of the plurality of nano-sized ceramic particles (12) and the plurality of micron-sized ceramic particles (20) is from about 10 to about 95%. The plurality of micron-sized ceramic particles (20) comprising one or more ceramic oxides, ceramic carbides, ceramic nitrides, ceramic borides, metal silicides, ceramic oxycarbides, ceramic oxynitrides or carbons. 10. Coating system according to 10. The coating system according to claim 1, wherein the coating system (10) is provided on the surface of an engineering component selected from the group consisting of gas turbine components, aircraft engine components, internal combustion engine components and cutting tool components.