CN100419105C - A kind of cermet material and its molding process - Google Patents

Abstract

The invention discloses a cermet material, which is mainly composed of titanium carbide, titanium nitride and metal bonding phase; the components are carbon 10.04-16.04%, titanium 60.07-67.07%, nickel 9.00-11.00%, molybdenum 7.50-12.50% , Nitrogen 1.60-5.20%. The invention also discloses the molding process of the above-mentioned material manufacturing products, including the process S1 to prepare the binder, S2 to obtain the injection molding blank, S3 to degrease the blank, S4 to sinter and post-treatment; wherein, in the S1 process, the composition of the binder Including 56# wax, microcrystalline wax, carnauba wax, high-density polyethylene, polypropylene, polyvinyl acetate, dibutyl phthalate, and stearic acid. Due to the low density and high strength of the material of the present invention, the manufactured product has the characteristics of light weight and high hardness; and its molding process adopts the metal powder injection molding process, which has the characteristics of low cost, easy processing and mass production.

Description

A kind of cermet material and its molding process

technical field

The invention provides a cermet material and a compact molding process for making products using the ceramic material. More specifically, the invention relates to a cermet material with TiC, TiN, Ni and Mo as main components and its forming process. .

Background technique

At present, the commonly used cermet materials are mainly concentrated on tungsten carbide, and its main component is composed of tungsten carbide and a certain binder phase metal (nickel, molybdenum, etc.). Tungsten carbide has relatively good properties in terms of hardness, toughness, and flexural strength. However, due to the high density of tungsten itself, the density of tungsten carbide materials has always been an important obstacle that limits its application. In 1950, titanium carbide-based cermets were successfully developed and used in metal cutting tools. The density of titanium carbide-based cermet is less than one-third of that of tungsten carbide, and it has high red hardness, good corrosion resistance, thermal conductivity and friction coefficient. However, due to the complex preparation technology of high-performance titanium carbide-based cermets, my country has not yet formed a finalized brand.

In addition, injection molding technology has been widely used, especially low-cost plastic products with complex shapes made by injection molding technology. Although these thermoplastic polymers are structurally inferior to other engineering materials (such as steel), they are still widely used. Mainly because these products are not only cheap but also complex in shape. Filling the polymer with dispersed metal or ceramic powder and then injecting is considered a way to improve strength. The latest development of this process is to maximize the solid powder content and exclude the polymer binder during sintering. This process can produce products with complex shapes, low cost and superior performance. Metal powder injection molding technology is a high-tech molding technology combining traditional powder metallurgy technology and plastic injection molding technology. It breaks through the limitations of the traditional metal powder compression molding process on the shape of the product, and can produce parts with complex shapes in large quantities and with high efficiency, reducing subsequent processing procedures.

The steps of manufacturing products by powder injection molding are as follows: select and configure the required powder; mix the powder with an appropriate amount of binder; make the mixture of powder and binder into uniform particle feed; inject the feed Form the blank in the closed mold cavity; remove the binder (degreasing) in the formed blank; densify the blank by high temperature sintering; further densify after sintering.

The main advantage of powder injection molding is the economical manufacture of high performance parts of complex shapes. In addition to the main advantages, this method has the following characteristics: the ability to form the final geometry with a minimum of mechanical processing; the better surface morphology of the product; compared with ordinary compression molding, it can reduce the friction between the powder and the wall The case where the density of the green compact is not uniform.

During the process of binder mixing, feeding and injection molding of blanks, the binder is a short-lived carrier that uniformly packs the powder into the desired shape and maintains that shape until sintering begins. The binder must be mixed with the powder to form a uniform feed for injection molding. The binder will affect the particle loading, agglomeration, compounding, molding, degreasing, dimensional accuracy, defects and final chemical properties of the molded body. The binder becomes The coordinator of each requirement factor.

During the degreasing process of the blank, the product blank goes through several different degreasing processes to remove the organic binder in the blank and maintain the geometric shape of the original blank in proportion. Degreasing is to remove the binder. Improper degreasing before sintering will lead to various defects such as blistering, deformation, and cracking of the blank. It is a process that requires skill to remove the binder without destroying the shape of the blank. For simple binder systems, it is most difficult to degrease without destroying the blank. The single-component binder must be further removed in a small temperature range, and the blank is easily damaged.

In the process of sintering and post-processing, the degreased product blank is sintered and densified in a vacuum sintering furnace to form a product compact, and after sintering, it is further densified by hot isostatic pressing to form a final product. Sintering essentially depends on the powder particle size, the size and shape of the compact, the sintering atmosphere, the sintering temperature, the holding time and the heating and cooling rate, etc. The pressure treatment after the voids of the sintered blank have been closed, that is, hot isostatic pressing, is processed after sintering to eliminate the voids.

Contents of the invention

The invention provides a cermet material with TiC, TiN, Ni, Mo as the main components and a precision molding process using the material to manufacture products, which solves the problem of metal materials with tungsten carbide as the main component in the prior art. The high density of tungsten makes its application limited; and the bending strength, fracture toughness and pore shape of other existing materials are not good, and the mechanical properties of the material are not high. In addition, the invention also solves the problems of difficulty in mass production due to the high hardness of the cermet material, and the problems of difficult processing and high manufacturing cost in the prior art.

In order to solve the above problems, a kind of cermet material of the present invention is mainly made of titanium carbide TiC phase, also includes titanium nitride TiN phase and the metal bonding phase mainly made of nickel Ni, molybdenum Mo; The cermet material The main components are: carbon C: 10.04% - 16.04%, titanium Ti: 60.07% - 67.07%, nickel Ni: 9.00% - 11.00%, molybdenum Mo: 7.50% - 12.50%, nitrogen N: 1.60% - —5.20%.

The precision molding process for manufacturing products based on the above-mentioned cermet materials is to prepare raw materials including titanium carbide TiC and titanium nitride TiN metal alloy powder; the process also includes: process S1 preparation of binder, S2 obtaining injection molding blank, S3 blank degreasing, S4 sintering and post-treatment; wherein, in the S1 process, the composition of the binder includes in the S1 process, the composition of the binder includes 20% to 30% of 56# wax, 15% to 25% of microcrystalline wax, 15%-25% palm wax, 8%-12% high-density polyethylene, 6%-10% polypropylene, 5%-9% polyvinyl acetate, 5%-9% phthalic acid Dibutyl ester, and 5% to 15% stearic acid as a plasticizer.

The improvement of the precision molding process of the above-mentioned cermet material is that the S3 process includes the process S31 solvent degreasing and S32 heating degreasing; in S31, the blank obtained in S2 is placed in n-ethane or trichloroethane between 50°C and 65°C Soak in organic solvent for 18 to 36 hours; in S32, place the blank after solvent degreasing in a vacuum sintering furnace, heat it to 320°C to 400°C in a vacuum environment, and keep it warm for 0.5 to 2 hours.

The improvement of the precision molding process of the cermet material also lies in that the soaking temperature and time in S31, and the heating temperature and time in S32 are proportional to the wall thickness of the blank; when the wall thickness of the blank is 5mm, the soaking temperature in S31 60-65° C. for 30-32 hours, and the heating temperature in S32 is 360-380° C. for 1.25 hours. When the blank wall thickness is 2 mm, the soaking temperature in S31 is 50-55° C. for 20-24 hours, and the heating temperature in S32 is 330-350° C. for 0.75 hours.

The improvement of the precision molding process of the cermet material also lies in that in the S2 process, the binder and the alloy powder in the S1 process are fully mixed at 100°C-200°C for 1-3 hours, and cooled after the mixing is completed, 18-36 After hours, it is crushed to make injection molding feed pellets: the feed pellets are then heated to the melting temperature in the injection barrel of the molding machine, and the reciprocating screw is used to gather, homogenize and pressurize the mixture, and finally obtain the injection molding blank .

The improvement of the precision molding process of the cermet material also lies in that the S4 process includes the vacuum sintering process S41 and the hot isostatic pressing process S42: in S41, after the S3 process is completed in the vacuum sintering furnace in S32, the temperature continues to rise to 1400° C. 1450°C, keep warm for 1-3 hours; after that, the blank is cooled with the furnace; in S42, place the blank in an argon environment, gradually pressurize to 60-180MPa, and gradually raise the temperature to 1250-1450°C, then maintain the pressure and temperature for 1 to 2 hours; then gradually reduce the pressure and cool with the furnace.

In the cermet material of the present invention, due to the adjustment of the ratio of TiC and TiN phases under the condition of determining the optimal total amount of ceramic phases, part of TiN is used to replace TiC, and the bending strength, fracture toughness and pore shape of the material are improved. . A reasonable proportion of Ti(C,N) cermet components can significantly improve the mechanical properties of the material, and the cermet material of the present invention has the characteristics of low density and high hardness, which is beneficial to the application of TiC-based composite cermet.

However, due to the high hardness and difficult processing of titanium carbide-based cermets in the present invention, in order to improve the forming accuracy of the finished product and reduce the machining allowance, the ceramic powder injection molding technology is adopted to reduce the processing difficulty, realize mass production, and save manufacturing cost. characteristics of cost. The products manufactured by using the above-mentioned materials and molding process have the characteristics of high hardness and light weight.

In addition, the setting of the binder in the molding process of the present invention improves the fluidity of the powder in the mold and increases the plasticity of the powder molding process. Compared with the binders commonly used in the prior art, it has high strength, can It has the advantages of no swelling and cracking after solvent degreasing, and the wall thickness of the injection blank can be greater than 5mm. Furthermore, the binder of the present invention can be removed in stages, with the remaining binder maintaining the integrity of the blank at each stage. Using the solvent extraction method can make the blank get out of the first component of the binder under the condition that the volume does not change substantially, and the damage to the blank can be minimized. The titanium carbide-based cermets of the invention can be used in the manufacture of spare parts such as watch cases and watch straps, as well as gas dynamic pressure bearing parts, precision knives and tools, and other fields.

Detailed ways

A cermet material and molding technology of the present invention will be described in detail below in conjunction with specific embodiments.

TiC-based cermets are carbide cermets that have been extensively studied and applied after WC cermets. The present invention mixes a part of TiN in the TiC powder, which can obviously improve the bending strength and the shape of the pores. And the present invention adopts Ni+Mo system as bonding metal, and allocates the bonding agent ratio of TiC-based cermet, obtains the material combination shown in the following table of its composition:

Material(%) C Ti Ni Mo N other upper limit 16.04 67.07 11.00 12.50 5.20 1.00 lower limit 10.04 60.07 9.00 7.50 1.60 0.00

The performance of the cermet material with the above composition can meet the following standards: density 5-6g/cm ³ , hardness not less than 1600kg/mm ² , flexural strength not less than 1400MPa, modulus of elasticity not less than 480GPa, and porosity reaching A02 .

The titanium carbide-based cermet of the invention can be mainly used in the manufacture of accessories such as watch cases and watch straps, as well as in the fields of gas dynamic pressure bearing parts, precision knives and tools. In the manufacture of products using cermet materials with the above components through the precision molding process, the present invention provides a relatively low-cost injection molding technology, which mainly includes the following processes: preparing a binder, obtaining an injection molding blank, degreasing the blank, and sintering And post-processing, in addition, before processing, prepare raw materials, including metal alloy powders of the above materials such as titanium carbide TiC and titanium nitride TiN.

First of all, before powder injection molding, it is necessary to add a certain amount of binder, which plays a decisive role in the conversion process of powder molding manufacturing products, and the binder of the present invention contains multiple groups of various additive phases sub-system. Including three waxes (56# wax + microcrystalline wax + palm wax), four polymers (high density polyethylene + polypropylene + polyvinyl acetate + dibutyl phthalate), a plasticizer ( stearic acid). Among them, the content of 56# wax is between 20% and 30%, the content of microcrystalline wax is between 15% and 25%, the content of palm wax is between 15% and 25%, and the content of high density polyethylene is between 8% and 12%. between 6% to 10% polypropylene, 5% to 9% polyvinyl acetate, 5% to 9% dibutyl phthalate, as a plasticizer The content of stearic acid is between 5% and 15%, and the content of plasticizer is adjusted according to the powder formula.

Second, precision molding to obtain injection molding blanks. Fully mix the binder and the alloy powder at 100°C to 200°C for 1 to 3 hours. The mixing time and temperature are proportional to the amount of powder and the content of plasticizer. After mixing, cool down and pulverize after 18 to 36 hours. Feed pellets into injection molding: The feed pellets are then heated to the melting temperature in the injection barrel of the molding machine, and the reciprocating screw is used to gather, homogenize and pressurize the mixture, and finally obtain the injection molding blank. During the preparation of cermets, the volume change is very significant, which can be as high as ten to twenty percent. The root cause is that after cermet molding, the filling density of the ceramic phase can only reach 50--70%, but after sintering, it can basically reach more than 99%. This process is completed through volume shrinkage. The invention finds out the regularity of dimension deformation through filling density of blank parts, changes during degreasing and sintering process, and shrinkage during sintering process, and reasonably designs molds to make the parts meet the design precision requirements.

Thirdly, the degreasing of blanks is a two-step degreasing process that combines the advantages of solvent degreasing and heating degreasing. The present invention adopts multi-component binder, and the degreasing process can be carried out step by step. At each step of debinding, the remaining binder will help maintain the integrity of the blank. However, for injection molding blanks using multi-component binders, the damage of the blanks is often easy to occur in the first step of degreasing, and the solvent extraction method can make the blanks with a small volume change. The first component in the degreasing process can minimize the damage to the blank during the degreasing process. Blank degreasing process of the present invention is designed as:

The first step is to use solvent degreasing, mainly to remove wax fat. Submerge the blank in an organic solvent (normal ethane or trichloroethane) and soak for 18 to 36 hours at 50°C to 65°C. The soaking time is proportional to the wall thickness of the part. Usually, when the wall thickness of the blank is 5mm, the soaking temperature is 60-65°C and the time is 30-32 hours; when the wall thickness of the blank is 2mm, the soaking temperature is 50-55°C and the time is 20-24 hours. parameter related.

The second step is heating and degreasing, which mainly removes other organic polymers in the binder. This step can be combined with the subsequent sintering process to complete it in one step. The blank after solvent degreasing is placed in a vacuum sintering furnace, heated to 320° C. to 400° C. in a vacuum environment, and kept for 0.5 to 2 hours. The heating temperature and heating time are directly proportional to the wall thickness of the part. Usually, when the wall thickness of the blank is 5mm, the heating temperature is 360-380°C and the time is 1.25 hours; when the wall thickness of the blank is 2mm, the heating temperature is 330-350°C and the time is 0.75 hours; the specific data is also related to other parameters related.

Finally, for sintering and post-processing, vacuum sintering or low-pressure hot isostatic pressing sintering is used to sinter the finished product. The heating degreasing and sintering process of the invention is completed in one step, and the sintered blank is subjected to hot isostatic pressing treatment to eliminate pores in the blank and achieve full densification of the material. The blank obtained after powder injection molding needs to be further sintered to increase its density, so as to meet the physical, chemical, mechanical and other requirements of the final product.

The first step is vacuum sintering. This sintering process and the heating and degreasing of the previous process can be completed in one step. First, the blank after solvent degreasing is placed in a vacuum sintering furnace, and heated to 320 ° C ~ 400 ° C in a vacuum environment. After 2 hours, the heating and degreasing process is completed. After that, continue to heat up to 1400 ℃ ~ 1450 ℃, and keep warm for 1 to 3 hours. The holding time is proportional to the wall thickness of the part; finally, the blank is cooled with the furnace.

The second step is hot isostatic pressing as post-sintering treatment. Place the parts in an argon environment, gradually pressurize to 60-180MPa, and gradually raise the temperature to 1250-1450°C, and keep the pressure and temperature for 1-2 hours; Then gradually reduce the pressure and cool with the furnace, and finally get a fully densified cermet product.

Claims (6)

1. a cermet material mainly is made of mutually titanium carbide, it is characterized in that, the thing that constitutes described cermet material also comprises titanium nitride phase and the metal bonding phase that mainly is made of nickel, molybdenum mutually; The main component of described cermet material is:

Carbon: 10.04%-16.04%,

Titanium: 60.07%-67.07%,

Nickel: 9.00%-11.00%,

Molybdenum: 7.50%-12.50%,

Nitrogen: 1.60%-5.20%.

2. precise forming technology about the described cermet material of claim 1, starting material comprise titanium carbide, titanium nitride metal alloy powders; Described technology comprises that also following operation: S1 preparation binding agent, S2 obtain injection molding blank, the degreasing of S3 blank, S4 sintering and aftertreatment, is characterized in that:

In the S1 operation, the composition of described binding agent comprises 20%～30% 56# wax, 15%～25% Microcrystalline Wax, 15%～25% palm wax, 8%～12% high density polyethylene(HDPE), 6%～10% polypropylene, 5%～9% polyvinyl acetate (PVA), 5%～9% adjacent phenylpropyl alcohol formic acid dibutylester, and as 5%～15% stearic acid of softening agent.

3. according to the precise forming technology of the described cermet material of claim 2, it is characterized in that described S3 operation comprises operation S31 solvent degreasing and S32 heating degreasing;

Between 50 ℃～65 ℃, place the organic solvent of hexane or trichloroethane to soak 18～36 hours the blank that obtains among the S2 among the S31;

Among the S32 blank after the solvent degreasing is placed in the vacuum sintering furnace, under vacuum environment, be heated to 320 ℃～400 ℃, be incubated 0.5～2 hour.

4. according to the precise forming technology of the described cermet material of claim 3, it is characterized in that, soaking temperature among the described step S31 and soak time are directly proportional with the blank wall thickness, when the blank wall thickness is 5 millimeters, soaking temperature is 60～65 ℃, and soak time is 30～32 hours, when the blank wall thickness is 2 millimeters, soaking temperature is 50～55 ℃, and soak time is 20～24 hours; Heating temperature among the described step S32 and heat-up time are directly proportional with the blank wall thickness, and when the blank wall thickness was 5 millimeters, Heating temperature was 360～380 ℃, be 1.25 hours heat-up time, when the blank wall thickness was 2 millimeters, Heating temperature was 330～350 ℃, and be 0.75 hour heat-up time.”

5. according to the precise forming technology of the described cermet material of claim 2, it is characterized in that, in the described S2 operation, with the binding agent of S1 operation and powdered alloy 100 ℃～200 ℃ following thorough mixing 1～3 hour, mix the postcooling that finishes, pulverize after 18～36 hours and make injection molding hello grain; Subsequently the feeding particle is heated to temperature of fusion in shaper injection gun barrel, adopts that reciprocating screw rod is assembled, homogenizing and pressurization compound, and finally obtain the injection molding blank.

6. according to the precise forming technology of the described cermet material of claim 2, it is characterized in that described S4 comprises vacuum sintering operation S41 and hot isostatic pressing operation S42:

Among the S41, finish follow-up continuing of S3 operation being warmed up to 1400 ℃～1450 ℃ in the vacuum sintering furnace in S32, be incubated 1～3 hour; After this blank furnace cooling;

Among the S42, blank is placed ar gas environment, progressively be pressurized to 60～180MPa, and after progressively being warming up to 1250 ℃～1450 ℃, keep-up pressure and temperature 1～2 hour; Progressively reduce pressure again and furnace cooling.