CN104372283A - Plasma sprayed TiN coating layer having relatively good hardness and toughness - Google Patents

Abstract

A plasma-sprayed TiN coating with good hardness and toughness. The invention discloses a TiN agglomerated powder. The powder includes atomic fractions of Ti-72% and N-28%, and the particle size formed after agglomeration is 40～ 80 μm spherical aggregates. The present invention also provides a TiN coating, which is prepared from TiN agglomerated powder; the three-peak phase of the coating is the TiN phase, and there are also some TiO, TiO2 and Ti3O oxide phases; the coating There is a layered distribution of light and dark phases in the coating, and there are a small amount of pores inside the layered structure and at the junction of the layered structure; there are no microscopic defects such as cracks at the junction of the coating and the substrate, and the combination is good. The invention adopts supersonic plasma spraying TiN coating, the hardness is high, can reach 1210HV _0.1 , the high hardness can improve the wear resistance of the coating, the fracture toughness of the coating is large, can improve the fracture mechanical properties of the coating, prolong the Coating fatigue life.

Description

A Plasma Sprayed TiN Coating with Better Hardness and Toughness

technical field

The invention relates to the field of material technology research, in particular to a plasma coating. the

Background technique

TiN coating has low coefficient of friction, high hardness, and good corrosion resistance, and is widely used as decorative coating, wear-resistant coating, and corrosion-resistant coating. At present, many researchers have prepared TiN coatings by reactive thermal spraying, chemical vapor deposition (CVD), physical vapor deposition (PVD), arc plating, etc. Research. The thickness of the TiN coating prepared by CVD, PVD and other technologies is thin, which reduces the mechanical properties of the coating; while the thermal spraying reaction technology can be used to prepare a thicker TiN coating, but the coating contains more pores and is more brittle. , The coating quality is not easy to control. The direct spraying of TiN powder by plasma spraying technology can prepare a thicker coating in a short time. At the same time, TiN is oxidized during the spraying process to produce Ti oxide phase, which can improve the toughness of the coating. the

Plasma spraying technology is widely used to prepare metal, ceramic and composite coatings to resist wear, corrosion and high temperature. During the spraying process, it is easy to produce microscopic defects such as oxides and pores. This is due to the chemical reaction of the molten particles with the surrounding medium during melting and flight and contact with the surface of the substrate, which makes the sprayed material oxidized, and also due to the molten particles. The continuous stacking and the rebound of some particles are lost, and pores inevitably appear between the particles. Microscopic defects such as oxide content and porosity in the coating are important criteria for judging the quality of the coating. Some scholars have studied the influence of oxide control and porosity on the performance of the coating during the plasma spraying process. By controlling the appropriate process parameter can significantly improve the microstructure and properties of the coating. TiN is easy to decompose and oxidize at high temperature, and has a high activity. It reacts with other media to form Ti oxides during the plasma spraying process. The Ti oxide phase has lower hardness and strength than the TiN phase, and the oxide content in the TiN coating is directly affect the coating performance. Fracture toughness is the ability of materials to resist fracture damage. The measurement of coating fracture toughness by indentation method has been widely used. Coating hardness and fracture toughness are the main indicators of coating resistance to crack proliferation and fracture, which directly affect the coating. service performance and lifespan. the

At present, many researchers have prepared TiN coatings by reactive thermal spraying, chemical vapor deposition (CVD), physical vapor deposition (PVD), arc plating, etc. Research. The thickness of the TiN coating prepared by CVD, PVD and other technologies is thin, which reduces the mechanical properties of the coating; while the thermal spraying reaction technology can be used to prepare a thicker TiN coating, but the coating contains more pores and is more brittle. , The coating quality is not easy to control. The direct spraying of TiN powder by plasma can ensure the thickness of the coating. At the same time, the oxide phase of Ti in the TiN coating can improve the toughness of the coating, thus obtaining a TiN coating with better toughness and hardness. the

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide a TiN coating. the

In order to realize the object of the present invention, the present invention provides a kind of TiN agglomeration powder, and this powder comprises atomic fraction is Ti-72% and N-28%, after its agglomeration forms spherical agglomerate with particle diameter of 40-80 μ m. the

Further, the present invention also provides a TiN coating, which is prepared from TiN agglomerated powder. the

Moreover, the three-peak phase of the coating is the TiN phase, and there are also some TiO, TiO2 and Ti3O oxide phases; there is a layered distribution of light and dark phases in the coating, and a small amount of Pores; there are no microscopic defects such as cracks at the junction of the coating and the substrate, and the combination is good. the

Preferably, the TiN coating is prepared by the following method:

A method for preparing a TiN coating, comprising the steps of:

(1) Preparation of TiN agglomerated powder: the powder includes atomic fractions of Ti-72% and N-28%, which form spherical aggregates with a particle size of 40-80 μm after agglomeration;

(2) Mold surface pretreatment;

(3) Spraying: Utilize a plasma spray gun for spraying, the spraying parameters are, the main gas for spraying is argon, the gas flow rate is 38L·min ⁻¹ -42L·min ⁻¹ ; the secondary gas is hydrogen, and the gas flow rate is 12L·min ⁻¹ −1 16L·min ^-1 ; the powder feeding gas is argon, the spraying distance is 100-140mm; the powder feeding amount is 40g·min ^-1 , the spraying voltage is 41KW-50KW; the spraying current is 500A-600A;

(4) Preparation of TiN coating: the three-peak phase of the coating is TiN phase, and part of TiO, TiO ₂ and Ti ₃ O oxide phases also exist.

Wherein, the TiN agglomerated powder is prepared by the following method:

(1-1) TiN powder raw material is atomized;

(1-2) The atomized TiN powder and binder are mixed and added to the agglomeration equipment for agglomeration, and the agglomerated powder is dried and cooled;

(1-3) Pass the agglomerated powder through a powder sieve of -200 mesh to 400 mesh, and the obtained TiN agglomerated powder has a particle size of 40-80 micron spherical agglomerates. the

The beneficial effects of the present invention are as follows:

The invention directly sprays the TiN powder, and can directly prepare a wear-resistant ceramic coating on the surface of the part, and the appearance of Ti oxide in the coating improves the toughness of the coating. Direct spraying of TiN coating can avoid the greater brittleness and complicated process of traditional reaction spraying TiN layer, which requires more manpower and material resources. the

The present invention adopts supersonic spraying TiN coating, the coating is denser, has a small amount of voids, is well combined with the substrate, and has a thickness of about 200 μm. The fracture toughness of the coating is measured by indentation method as

The invention adopts the TiN coating prepared by plasma spraying TiN powder, and the method can be directly sprayed by powder, which is convenient to operate, easy to popularize, and greatly saves cost. the

The invention adopts supersonic plasma spraying TiN coating, the hardness is high, can reach 1210HV _0.1 , the high hardness can improve the wear resistance of the coating, the fracture toughness of the coating is large, can improve the fracture mechanical properties of the coating, prolong the Coating fatigue life.

Description of drawings

The TiN coating that Fig. 1 embodiment of the present invention 1 makes;

The XRD test result of Fig. 2 coating;

The SEM scanning morphology of the coating in Fig. 3;

Fig. 4 coating hardness test result;

Figure 5 Fracture toughness test indentation morphology;

The influence of Fig. 6 different porosity on coating hardness;

Figure 7 Effect of different oxide contents on the fracture toughness of the coating. the

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments thereof. But the scope of protection of the present invention is not limited to the following examples, and should include all content in the claims. the

All used in the following examples are conventional instruments and equipment. the

The preparation of embodiment 1 coating

The preparation process of the coating is divided into four stages: preparation of TiN agglomerated powder, mold surface pretreatment, spraying parameter optimization, and spraying. The steps of the four stages are as follows:

(1) Prepare TiN agglomerated powder;

(1-1) Atomize TiN powder with a particle size of 1-5 μm as raw material;

(1-2) Mix the atomized TiN powder and binder into the atomization equipment for agglomeration, dry the agglomerated powder, and granulate;

(1-3) passing the agglomerated powder through a -200 mesh to +400 mesh powder sieve to obtain a TiN agglomerated powder with a particle size of 40-80 micron micron spherical agglomerates. the

The powder includes atomic fractions of Ti-72% and N-28%, and after agglomeration, spherical agglomerates with a particle diameter of 40-80 μm are formed. the

(2) Mold surface pretreatment;

(2-1) Grinding the mold surface first, so that the roughness of the mold surface reaches Ra=0.8μm;

(2-2) Carry out alcohol or acetone cleaning to mold surface then, remove the oil stain on mold surface;

(2-3) Perform sandblasting on the surface of the mold. The sandblasting material is brown corundum with a particle size of less than 700 μm. The sandblasting air pressure is 0.7MPa, the sandblasting angle is 45°, and the distance between the spray gun and the mold surface is 0.15m. the

(3) Spraying

(3-1) The spraying equipment adopts a supersonic plasma spray gun, and the spraying parameters are as follows: the main spraying gas is argon (38L·min ^-1 ), the secondary gas is hydrogen (16L·min ^-1 ), and the powder feeding gas is argon, The spraying distance is 125mm, the powder feeding volume is 40g·min ^-1 , the spraying voltage is 46KW, and the spraying current is 540A;

(3-2) Under the spraying parameters, use a supersonic plasma spray gun to spray on the surface of the workpiece. The scanning process uses "well" character scanning, and the scanning speed is 1.25m/min;

(3-3) Carry out 4 to 6 "well" scans on the surface of the workpiece according to the deposition rate to obtain a coating with a thickness of about 200 μm;

(4) Prepare TiN coating

(4-1) The melting point of TiN powder is about 2950°C. Spray powder TiN agglomerated powder is melted at the high temperature of the plasma beam. The supersonic plasma spraying equipment can make the molten powder have a high flying speed and form a denser coating;

(4-2) Due to the deposition of the spray powder on the substrate, the molten particles reacted with the surrounding air during the flight, resulting in oxidation, and formed TiO, Ti ₃ O, TiO ₂ oxides, Ti oxide phases It has lower strength and hardness than TiN phase, which can improve the toughness of the coating.

The prepared TiN coating is shown in Figure 1. The coating is relatively dense, has a small amount of voids, and is well combined with the substrate. The thickness is about 200 μm. The fracture toughness of the coating measured by the indentation method is

The performance of coating in embodiment 2 embodiment 1

In order to measure phase composition and phase structure in coating, adopt BRUKER company D8 type X-ray analysis diffractometer (XRD) to carry out phase composition analysis to the coating that embodiment 1 makes, diffraction target material is Cu target, and wavelength is 0.154056nm, The test results are shown in Figure 2. the

Figure 2 shows the XRD spectrum of the TiN coating. After comparing the PDF card, the three strong peak phases in the figure are the TiN phase. The TiN phase has a strong (200) orientation, and there are some TiO, TiO ₂ and Ti ₃ O oxide phases. , which is due to the oxidation of TiN at high temperature during the plasma spraying process to form Ti oxides. The existence of TiO and Ti ₃ O metastable phases in the coating is due to the insufficient deposition of TiN during the plasma spraying process. The intensity of the triple peak of the TiN phase is much greater than that of the oxide phase, indicating that the coating is mainly composed of the TiN phase.

In order to determine the distribution of each element in the coating, the EDS energy spectrometer used in the Nova NanoSEM450 scanning electron microscope was used to analyze the elements of the TiN coating, as shown in Figure 3 and Table 1, to determine the elements in the coating. The connection between the phases. the

Table 1 Coating EDS results

It can be seen from the cross-sectional scanning photo in Figure 3 that there is a layered distribution of light and dark phases in the coating, and there are a small amount of pores inside the layered structure and at the junction of the layered structure. From the element surface scanning distribution diagram, it can be seen that the Ti element is evenly distributed in the entire section, and the N element and O element are regionally distributed. In the SEM image, the darker A area is rich in Ti and N, and a small amount of O, on the contrary, the brighter B region is rich in Ti, O and a small amount of N. Combined with the XRD results, it can be analyzed that the main component of area A is TiN phase, while the main component of area B is Ti oxide phase and a small amount of TiN phase. The difference in color between A and B may be mainly due to the difference in the content of the oxide phase. the

HVS-1000 digital display Vickers hardness tester is used to test the microhardness of the coating. The microhardness load is 100g, the loading time is 15S, the number of test points is 10 points, and the average hardness of the coating reaches 1210HV _0.1 . You can see The resulting coating has relatively high hardness, as shown in Figure 4.

The HVS-1000 digital display Vickers hardness tester was used to press out the indentation, as shown in Figure 5 and Table 2, and the fracture toughness of the coating was calculated using the following formula of the indentation method:

$\mathrm{<span\; class="notranslate">\; Hv</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 0.4636</span>}\mathrm{<span\; class="notranslate">\; P</span>}}{{\mathrm{<span\; class="notranslate">\; a</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; IC</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 0.016</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; )</span>}^{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; P</span>}}{{\mathrm{<span\; class="notranslate">\; c</span>}}^{\frac{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In formula (1): a is half of the length of the diagonal indentation; P is the loading load; in formula (2): E is Young's modulus; c is the length of the radial crack from the center of the indentation to the edge of the crack. the

Table 2 Calculation parameters of coating fracture toughness K _IC

Influence of spraying parameters in the coating on porosity and oxides, also on hardness and fracture toughness

The trend diagram of the influence of oxide and porosity in the coating on the hardness is shown in Figure 6. It can be seen that under the three processes, the hardness of the coating decreases significantly with the increase of the inner and porosity of the coating. When the porosity is small, the hardness of the coating is the highest, which is 1402HV0.1. the

The influence trend of oxide and porosity in the coating on fracture toughness is shown in Fig. 7. It can be seen that as the oxide content increases, the fracture toughness of the coating increases first and then decreases. When the oxide content is about 16%, the fracture toughness of the coating is the largest, which is

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. These improvements and modifications It should also be regarded as the protection scope of the present invention. the

Claims (5)

1. A TiN agglomerated powder, characterized in that the powder comprises atomic fractions of Ti-72% and N-28%, and after agglomeration, spherical agglomerates with a particle size of 40-80 μm are formed. 2. A TiN coating, characterized in that the TiN coating is prepared from TiN agglomerated powder. 3. TiN coating as claimed in claim 2, is characterized in that, this TiN agglomeration powder is to be prepared by following method: (1-1) TiN powder raw material is atomized; (1-2) Mixing the atomized TiN powder and binder into the atomization equipment for agglomeration, drying the agglomerated powder, and granulating; (1-3) The agglomerated powder is passed through a powder sieve of -200 mesh to +400 mesh, and the obtained TiN agglomerated powder has a particle size of 40-80 micron spherical agglomerates. 4. TiN coating as claimed in claim 2, is characterized in that, the three strong peak phases of this coating are TiN phase, also have part TiO, TiO2 and Ti3O oxide phase; Exist light and dark phase lamellar in this coating Distribution, there are a small amount of pores inside the layered structure and at the junction of the layered structure; there are no microscopic defects such as cracks at the junction of the coating and the substrate, and the combination is good. 5. TiN coating as claimed in claim 2 or 4 is characterized in that, this coating is prepared by following method: (1) Preparation of TiN agglomerated powder: the powder includes atomic fractions of Ti-72% and N-28%, which form spherical agglomerates with a particle size of 40-80 μm after agglomeration; (2) Mold surface pretreatment; (3) Spraying: Utilize a plasma spray gun for spraying, the spraying parameters are, the main gas for spraying is argon, the gas flow rate is 38L·min ⁻¹ -42L·min ⁻¹ ; the secondary gas is hydrogen, and the gas flow rate is 12L·min ⁻¹ −1 16L·min ^-1 ; the powder feeding gas is argon, the spraying distance is 100-140mm; the powder feeding amount is 40g·min ^-1 , the spraying voltage is 41KW-50KW; the spraying current is 500A-600A; (4) Preparation of TiN coating: the three-peak phase of the coating is TiN phase, and part of TiO, TiO ₂ and Ti ₃ O oxide phases also exist.