Preparation method of carbide-enhanced Ni / Cr composite binding phase Cr3C2-based metal ceramic

Abstract

The invention discloses a preparation method of carbide-enhanced Ni / Cr composite binding phase Cr3C2-based metal ceramic, and belongs to the field of composite materials. The preparation method is characterized by comprising the following steps: firstly, respectively weighing 0 to 25 weight percent of binder metal powder, 0 to 16 weight percent of second-phase carbide powder, 0 to 1 weight percent of carbon supplementing agent carbon powder and the balance of chromium carbide (Cr3C2) powder; the carbide-enhanced Ni / Cr composite binding phase Cr3C2-based metal ceramic is prepared through traditional powder metallurgy processes such as chromium carbide-second phase carbide pre-ball-milling, mixed material ball-milling, ball-material separation, drying and sieving, glue mixing and granulation, compression molding, vacuum pressureless sintering and the like. The Ni / Cr composite metal powder is used as a binder, the second-phase carbide is used as a modifier, and the carbon powder is used as a carbon supplement agent, so that the problems that the market price of binder metal nickel is relatively high, domestic mineral resources are scarce, a decarburization phase is easily generated in the sintering process of Cr3C2 in industrial production, grains grow abnormally and the like are solved; on the basis of ensuring the wear resistance and corrosion resistance of the chromium carbide-based metal ceramic, certain hardness is improved, and the chromium carbide-based metal ceramic is suitable for the fields of cutting tools, wear-resistant and corrosion-resistant parts and the like.

Description

Technical Field

[0001] The invention relates to a method for preparing a metal ceramic material, in particular to a method for preparing a carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based metal ceramic, belonging to the field of composite materials. Background Art

[0002] Cermets are composite hard materials made of one or more refractory metal carbides and bonding metals through powder metallurgy. They have the advantages of both ceramics and metals and have excellent comprehensive properties. Traditional WC-based cermets are widely used in cutting and mining tools due to their high hardness, high strength and good fracture toughness. However, WC-based cermets have poor acid and alkali corrosion resistance and high-temperature oxidation resistance, which limits their further industrial application. In addition, in view of the international problem of resource shortage of elements such as W, Ti, and Co, research and development of cermet composite materials that can replace these elements has great economic benefits and development prospects. Among the global mineral resources, elements such as Cr, Ni, and Mo are relatively abundant. With Cr carbides replacing WC, TiC, etc. as hard phases and metal Ni replacing Co as metal bonding phases, chromium carbide-nickel cermets came into being. Although the research on chromium carbide (Cr3C2)-based metal ceramics started late, compared with traditional (TiC, WC)-Co-based metal ceramic composites, it still has superior properties such as low density, high high-temperature hardness, high thermal expansion coefficient, good high-temperature oxidation resistance, excellent wear resistance, and good corrosion resistance.

[0003] CN116287924A discloses a toughened chromium carbide-based metal ceramic and a preparation method thereof, wherein Cr2O3, TiO2, WO3 and carbon black are used as raw materials for a carbon thermal reduction reaction, and Ti and W atoms are dissolved into the Cr3C2 lattice during the carbon thermal reduction reaction, thereby obtaining a (Cr, Ti, W)3C2 composite solid solution powder with a single phase composition; then, the powder is mixed with Ni powder and a molding agent to prepare the chromium carbide-based metal ceramic; wherein the hard phase (Cr, Ti, W)3C2 effectively reduces the dissolution rate of Cr3C2 in the bonding phase Ni, inhibits the growth of the hard phase grains and eliminates the pores, and at the same time, the lattice distortion effect produced by the powder strengthens the carbon fixing ability of the Cr3C2 matrix, effectively inhibits the generation of the carbon-deficient phase, and has a positive effect on the formation of a relatively uniform hard phase grain structure, thereby achieving a simultaneous improvement in the strength, hardness and toughness of the chromium carbide-based metal ceramic.

[0004] Chromium carbide-based metal ceramics are currently widely used in the field of coatings due to their excellent corrosion resistance and high-temperature oxidation resistance. CN112779451B discloses a chromium carbide metal ceramic composite powder, coating and preparation method thereof. In terms of mass fraction, the components in the powder are Cr3C2: 63.75-67.5%, Ni: 17-18%, Cr: 7.29-8.43%, Co: 6.58-9.87%, and Mo: 0.63-0.95%. The above composite powder is sprayed by a supersonic spraying system to prepare a chromium carbide metal ceramic composite coating, which has good density and bonding strength. Compared with traditional nickel-chromium-chromium carbide (Cr3C2-NiCr) coatings, this coating has significantly improved in terms of high-temperature oxidation resistance, wear resistance and other properties, and can be used for the repair and strengthening of fluidized bed burners, nozzles, boiler components, pipelines and other components.

[0005] However, the current chromium carbide-based cermets have poor powder sintering properties during the preparation process, resulting in technical problems such as uneven grain size, excessive pores, and poor wear resistance of the prepared cermets. In addition, it also involves the use of a large amount of strategic resources (such as Ni, W, etc.), which increases the production cost. Therefore, it is necessary to develop new cermet preparation processes and component formulas that improve the sintering properties of cermet powders and reduce the use of strategic resources. Summary of the invention

[0006] The present invention aims at the problem that the powder sintering property of the current chromium carbide-based metal ceramic preparation process is poor, its hardness and wear resistance are different from those of traditional metal ceramics, and the problem that simple chromium carbide powder (Cr3C2) is prone to decarburization during sintering. The present invention provides a chromium carbide-based metal ceramic hard material and its production process, which has a cheaper binder material cost, is more friendly to human health and the ecological environment, has better sintering performance, effectively inhibits decarburization behavior, and can ensure that the mechanical properties are not deteriorated. To achieve the above purpose, the technical solution adopted by the present invention is: metal Cr partially replaces Ni as a binder to reduce the use of strategic resources and to a certain extent improve the hardness of the material; a second phase carbide (one or more of TiC, Mo2C, TaC, NbC, WC and VC) is added to refine the grains and improve the performance of the metal ceramic; carbon powder is used as a carbon supplement to inhibit the decarburization behavior of the chromium carbide-based metal ceramic during the sintering process.

[0007] The method for preparing the carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based cermet of the present invention is characterized by comprising the following steps in sequence: (1) Ingredients: Weigh Cr3C2 powder, second phase carbide powder (one or more of TiC, Mo2C, TaC, NbC, WC and VC), metal binder powder (Ni-Cr), and carbon filler (C) in the following mass ratios: (50wt.%~90wt.%): (0wt.%~20wt.%): (5wt.%~30wt.%): (0wt.%~1wt.%). (2) Pre-milling: The weighed Cr3C2 and second phase carbide powders are subjected to planetary ball milling. The ball milling medium is anhydrous ethanol. The ball milling speed is 300-400 r / min. The mass ratio of raw material powder to grinding ball is 1:(5-10), the volume ratio of raw material to ball milling medium is 1:(2-5), and carbide grinding balls with a mass ratio of large to small balls of 1:(8-12) are used. The ball milling time is 6-24 h. (3) Mixing ball milling: After the pre-milling, add the weighed other raw material powders into the stainless steel ball mill for pre-milling. The ball milling parameters are the same as those in the pre-milling process to ensure that the raw material powders are fully ground, crushed, dispersed and mixed. (4) Ball material separation: After the ball milling is completed, the mixed slurry in the ball mill is filtered through a sieve of not less than 400 mesh to remove the grinding balls and possible cemented carbide debris. The filtered wet material is placed in a drying oven at 80°C for 3 hours. After the anhydrous ethanol is completely volatilized, the agglomerated mixed material is passed through a sieve of not less than 200 mesh to obtain a chromium carbide-nickel chromium-carbide mixed powder. (5) Rubber-blending granulation: Rubber and solvent oil are mixed and stirred at a volume ratio of 1:2 for 1 hour to obtain a molding agent. In order to improve the molding ability of the powder, a molding agent is added to the mixed powder, mixed thoroughly to ensure that the molding agent is evenly coated on the surface of the particles, and placed in a 75°C drying oven for 2 hours. The fully dried sample is passed through a sieve of not less than 80 mesh to obtain a rubber-blended mixed powder. (6) Compression molding: Weigh an appropriate amount of the glue-doped mixed powder in step (5) and place it into a compression mold. Maintain the pressure at a pressure of 10 to 30 MPa for not less than 1 minute. After the pressure is released, demold the mold to obtain a carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based metal ceramic green body. (7) Vacuum sintering: Place the green body in a vacuum sintering furnace for sintering at a heating rate of 4-10°C / min, keep it at 500-550°C for 30-60min, keep it at 1000-1200°C for 30-60min, keep it at 1200-1370°C for 40-80min, and then cool it to room temperature. Finally, a carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based cermet material is obtained.

[0008] The method for preparing the carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based cermet of the present invention is further characterized by: (1) When ball milling the mixed materials, the added ball milling medium should completely cover the grinding balls and abrasives, and the parameters such as ball milling time and ball milling speed should be reasonably designed according to the amount and particle size of the abrasives to ensure that the abrasives are fully ground and crushed, and the various components are evenly mixed, so as to avoid poor ball milling effect due to unreasonable design of ball milling parameters. (2) When adding the molding agent, quickly mix the molding agent and powder manually and evenly, with the addition amount of 1-2 ml / g to ensure that the molding agent can be evenly attached to the surface of the powder particles before the solvent oil in the molding agent evaporates, to avoid the solvent oil volatilization and powder agglomeration caused by too long mixing time, which requires continued addition of molding agent. If too much molding agent is added, bulging or cracks may occur after sintering. (3) When sintering carbide-reinforced Ni / Cr composite binder phase Cr3C2-based cermet, the initial vacuum degree of vacuum sintering is 1Pa, and the vacuum degree during sintering should be less than 10 -2 Pa.

[0009] The present invention has the following advantages: (1) it is prepared by using traditional powder metallurgy technology, the process is simple and mature, the cost is low, and it is conducive to industrial production; (2) the chromium carbide powder and the second-phase carbide powder are pre-milled before the mixed material is ball-milled to make them fully mixed, which is beneficial to diffusion and mass transfer in the later sintering process; (3) the addition of the second-phase carbide can form a solid solution with the chromium carbide, which has a solid solution strengthening effect, and can form a segregation film on the surface of the chromium carbide to prevent abnormal growth of grains; (4) since chromium carbide is easy to decarburize during the sintering process, the present invention uses carbon powder as a carbon supplement to avoid the generation of a carbon-deficient phase during the sintering process. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the preparation process of the carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based cermet of the present invention;

[0010] Figure 2 It is a schematic diagram of sintering parameters in the sintering process of the carbide reinforced Ni / Cr composite bonding phase Cr3C2-based metal ceramic of the present invention. Specific implementation methods

[0011] Example 1: Carbide-reinforced Ni / Cr composite binder phase Cr3C2-based cermet material was prepared according to the following steps: (1) Ingredients: Weigh Cr3C2 powder, second phase carbide (Mo2C) powder, metal binder (Ni-Cr) powder, and carbon replenisher (C) in a mass ratio of 66.6wt.%: 8wt.%: 25wt.%: 0.4wt.%, respectively. (2) Pre-milling: The weighed Cr3C2 and Mo2C powders were subjected to planetary ball milling. The ball milling medium was anhydrous ethanol. The ball milling speed was 350 r / min. The mass ratio of raw material powder to grinding ball was 1:10, and the volume ratio of raw material to ball milling medium was 1:3. Carbide grinding balls with a mass ratio of large to small balls of 1:9 were used. The ball milling time was 24 h. (3) Mixing ball milling: After the pre-milling, add the weighed other raw material powders into the stainless steel ball mill for pre-milling. The ball milling parameters are the same as those in the pre-milling process to ensure that the raw material powders are fully ground, crushed, dispersed and mixed. (4) Ball material separation: After the ball milling is completed, the mixed slurry in the ball mill is filtered through a 400-mesh screen to remove the grinding balls and possible cemented carbide debris. The filtered wet material is placed in a drying oven at 80°C for 3 hours. After the anhydrous ethanol is completely volatilized, the agglomerated mixture is passed through a 200-mesh screen to obtain a chromium carbide-nickel chromium-carbide mixed powder. (5) Rubber-blending granulation: Rubber and solvent oil were mixed and stirred at a volume ratio of 1:2 for 1 hour to obtain a molding agent. In order to improve the molding ability of the powder, a molding agent was added to the mixed powder, mixed thoroughly to ensure that the molding agent was evenly coated on the surface of the particles, and placed in a 75°C drying oven for 2 hours. The fully dried sample was passed through an 80-mesh sieve to obtain a rubber-blended mixed powder. (6) Compression molding: Weigh an appropriate amount of the glue-doped mixed powder in step (5) and put it into a compression mold. Maintain the pressure at 15 MPa for 1 min, release the pressure and demold to obtain a carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based metal ceramic green body. (7) Vacuum sintering: The green body is placed in a vacuum sintering furnace for sintering at a heating rate of 5°C / min, and kept at 550°C for 40min, 1100°C for 40min, and 1250°C for 60min, and then cooled to room temperature. Finally, a carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based cermet material is obtained.

[0012] Example 2: Carbide-reinforced Ni / Cr composite binder phase Cr3C2-based cermet material is prepared according to the following steps: (1) Ingredients: Cr3C2 powder, second phase carbide (Mo2C, VC) powder, metal binder (Ni-Cr) powder, and carbon filler (C) were weighed separately, and their mass fraction ratios were 69.4wt.%: 10wt.%: 20wt.%: 0.6wt.%. (2) Pre-milling: The weighed Cr3C2, Mo2C and VC powders were subjected to planetary ball milling. The ball milling medium was anhydrous ethanol. The ball milling speed was 300 r / min. The mass ratio of raw material powder to grinding ball was 1:10, and the volume ratio of raw material to ball milling medium was 1:5. Carbide grinding balls with a mass ratio of large to small balls of 1:9 were used. The ball milling time was 20 h. (3) Mixing ball milling: After the pre-milling, add the weighed other raw material powders into the stainless steel ball mill for pre-milling. The ball milling parameters are the same as those in the pre-milling process to ensure that the raw material powders are fully ground, crushed, dispersed and mixed. (4) Ball material separation: After the ball milling is completed, the mixed slurry in the ball mill is filtered through a 400-mesh screen to remove the grinding balls and possible cemented carbide debris. The filtered wet material is placed in a drying oven at 80°C for 3 hours. After the anhydrous ethanol is completely volatilized, the agglomerated mixture is passed through a 200-mesh screen to obtain a chromium carbide-nickel chromium-carbide mixed powder. (5) Rubber-blending granulation: Rubber and solvent oil were mixed and stirred at a volume ratio of 1:2 for 1 hour to obtain a molding agent. In order to improve the molding ability of the powder, a molding agent was added to the mixed powder, mixed thoroughly to ensure that the molding agent was evenly coated on the surface of the particles, and placed in a 75°C drying oven for 2 hours. The fully dried sample was passed through an 80-mesh sieve to obtain a rubber-blended mixed powder. (6) Compression molding: Weigh an appropriate amount of the glue-doped mixed powder in step (5) and put it into a compression mold. Maintain the pressure at 12 MPa for 2 minutes. Release the pressure and demold the mold to obtain a carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based metal ceramic green body. (7) Vacuum sintering: The green body is placed in a vacuum sintering furnace for sintering at a heating rate of 10°C / min, and is kept at 500°C for 45min, 1000°C for 45min, and 1300°C for 60min, and then cooled to room temperature with the furnace. Finally, a carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based cermet material is obtained.

[0013] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A carbide reinforced Ni / Cr composite bonding phase Cr3C2 based cermet material, characterized in that: According to mass percentage, it is composed of nickel / chromium metal bonding phase: 5wt.%~30wt.%, second phase carbide: 0wt.%~20wt.%, carbon replenisher: 0wt.%~1wt.%, and the remainder is chromium carbide (Cr3C2) hard phase, and the sum of the mass percentages of each component is 100wt.%.

2. The carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based cermet material and its preparation method according to claim 1, characterized in that: The second phase of carbide is one or more of TiC, Mo2C, TaC, NbC, WC and VC; the metal bonding phase is Ni-Cr, which is added in the form of Ni and Cr metal elements; the hard phase is Cr3C2 powder; and the carbon supplement is C powder.

3. A carbide reinforced Ni / Cr composite bonding phase Cr3C2 based metal ceramic material and a preparation method thereof according to claim 1 or 2, characterized in that: The following steps are included in sequence: (1) Ingredients: Weigh Cr3C2 powder, second phase carbide powder, metal binder powder, and carbon filler respectively, and the mass ratio thereof is (50wt.%~90wt.%):(0wt.%~20wt.%):(5wt.%~30wt.%):(0wt.%~1wt.%); (2) Pre-milling: The weighed Cr3C2 and second-phase carbide powders are subjected to planetary ball milling. The ball milling medium is anhydrous ethanol. The ball milling speed is 300-400 r / min. The mass ratio of raw material powder to grinding ball is 1:(5-10), the volume ratio of raw material to ball milling medium is 1:(2-5), and the cemented carbide grinding balls with a mass ratio of large to small balls of 1:(8-12) are used. The ball milling time is 6-24 h. (3) Mixing ball milling: After the pre-milling, the other raw material powders are weighed and added to the stainless steel ball mill for pre-milling. The ball milling parameters are the same as those in the pre-milling process to ensure that the raw material powders are fully ground and evenly mixed. (4) Ball material separation: After the ball milling is completed, the mixed slurry in the ball mill is filtered through a sieve of not less than 400 mesh to remove the grinding balls and possible cemented carbide debris. The filtered wet material is placed in a drying oven at 80°C for 3 hours. After the anhydrous ethanol is completely volatilized, the agglomerated mixture is passed through a sieve of not less than 200 mesh to obtain a chromium carbide-nickel chromium-carbide mixed powder; (5) Rubber-blending granulation: Rubber and solvent oil are mixed in a volume ratio of 1:2, and stirred for 1 hour using a magnetic stirrer to obtain a molding agent. In order to improve the molding ability of the powder, a molding agent is added to the mixed powder, and the mixture is fully mixed to ensure that the molding agent is evenly coated on the surface of the particles, and then placed in a 75°C drying oven for 2 hours. The fully dried sample is passed through a sieve of not less than 80 mesh to obtain a rubber-blended mixed powder; (6) Compression molding: Weighing a suitable amount of the glue-doped mixed powder in step (5) and placing it into a compression mold, maintaining the pressure at a pressure of 10 to 30 MPa for not less than 1 minute, and demolding after pressure release to obtain a carbide-reinforced Ni / Cr composite binder phase Cr3C2-based metal ceramic green body; (7) Vacuum sintering: Place the green body in a vacuum sintering furnace for sintering at a heating rate of 4-10°C / min, keep it at 500-550°C for 30-60min, keep it at 1000-1200°C for 30-60min, keep it at 1200-1370°C for 40-80min, and then cool it to room temperature. Finally, a carbide-reinforced Ni / Cr composite bonding phase Cr3C2-based cermet material is obtained.

4. The carbide-reinforced Ni / Cr composite binder phase Cr3C2-based cermet material and preparation method thereof according to claim 3, further characterized by: (1) When the mixed materials are ball-milled, the added ball-milling medium should completely cover the grinding balls and abrasives, and the parameters such as ball-milling time and ball-milling speed should be reasonably designed according to the amount and particle size of the abrasives to ensure that the abrasives are fully ground and crushed, and the various components are evenly mixed, so as to avoid poor ball-milling effect due to unreasonable design of ball-milling parameters; (2) When mixing the molding agent, the molding agent and the powder are quickly and manually mixed evenly, and the mixing amount is 1-2 ml / g to ensure that the molding agent can be evenly attached to the surface of the powder particles before the solvent oil in the molding agent evaporates, so as to avoid the solvent oil volatilization and powder agglomeration caused by too long mixing time. The molding agent needs to be continuously added, which makes the molding agent too much, and bulging or cracks may appear after sintering; (3) When sintering carbide-reinforced Ni / Cr composite binder phase Cr3C2-based cermet, the initial vacuum degree of vacuum sintering is 1Pa, and the vacuum degree during sintering should be less than 10 -2 Pa.

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