RU2538743C2 - Production of parts from powders of compounds of carbide series and binder to this end - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to powder metallurgy, particularly, to methods of producing various articles from carbide-based solid alloys. Temporary binder containing two-component dispersant and two-component lubing additive are mixed at 1:3.6 to 1:13.1 ratio with mix of inorganic powders including powders of carbides and contact binder. Part is moulded and temporary binder is thermally removed in two steps in vacuum. At first step, residual pressure is kept equal to 13-1.3 Pa at heating from room temperature to 300°C while at second step - at 1.3-0.13 Pa at heating from room temperature to 1370-1390°C. Part is sintered at inert gas overpressure at 1370-1390°C.

EFFECT: power and material savings, high operating qualities.

9 cl, 1 tbl, 1 ex

Description

The invention relates to the field of powder metallurgy, namely, the technology for the production of products by extrusion or pressing of powders of inorganic materials based on carbides and the subsequent thermal removal of the temporary binder at a low residual pressure and sintering of the body of the product at an inert gas overpressure. The method relates to energy and resource-saving technologies for hard alloy products and requires only finishing processing of the product, while ensuring high performance characteristics of the final product. The quality of the sintered product is determined by the presence of inhomogeneities, pores, un relaxed mechanical stresses, mismatch of the lattice parameters of the conjugated inorganic materials. Pores and inhomogeneities are caused, on the one hand, by the choice of a binder that ensures the homogenization of the mixture and its ability to form, on the other hand, by the technological method of its removal.

The compositions and ratios of the components of inorganic fillers of single carbide, two carbide and three carbide hard alloys with a constant cobalt binder are known, the influence of the degree of dispersion of the refractory phase on the physicochemical and mechanical properties of the final product is known, for example, from the Simstal hard alloys survey material (http: // simstal.ru/ri/material/tviordye-splavy), the properties of which are given in the table for comparison.

A close analogue of the proposed technical solution providing a quality product by powder metallurgy may be RF patent No. 2046114, publication date 20.101995, IPC С04В 35/00, patent holder Hekhst A.G. the name "Molding mass and method of its preparation", in which the molding mass, comprising a ceramic or metal powder filler, a melt of wax and a copolymer of ethylene vinyl acetate, organic peroxides, is mixed and conditions are created for polymerization and form fixing of the product, they are subjected to thermal removal of the temporary binder in the medium, enriched with oxygen, at a speed of 2 to 5 ° C / min to a temperature of 1400 ° C and sinter. The disadvantage of this technical solution is the strict requirements for the physicochemical properties of the nomenclature of the starting ligaments, the need for oxygen for their thermal removal at overpressure.

The closest analogue of the proposed technical solution is RF patent No. 2169056, publication date 06/20/2001, IPC B22F3 / 20, applicant Carpenter Technology Corporation (US) “Method for manufacturing parts from inorganic powder material (options) and a binder composition for implementing the method” , which use a multicomponent binder, introduced in the molten form. The main criterion for the selection of binder components is the ratio of the pressure of their saturated vapors at the most unstable decomposition temperature, which ensures the gradual removal of the temporary binder as the sintering temperature increases at a speed of 0.5-10 ° C / min, in addition, holding at a maximum temperature of 180 min is possible . Total sintering time is less than 12 hours. The disadvantage of this technical solution is that the heat treatment to remove the binder and sintering is carried out in a single process, which is not economically feasible, because equipment that is less expensive to operate can be used in the low-temperature binder removal section; moreover, it is more expedient to remove the binder in a vacuum environment, which ensures the compaction of the body of the part.

The aim of the present invention is energy and resource saving, while maintaining the achieved quality, the use of a nomenclature of components of a temporary bundle that are not classified as harmful or dangerous.

The problem is solved by removing the binder in two stages, which ensures:

- differential loading of vacuum equipment: for the low-temperature stage of binder removal, a vacuum oven is used, and for a high-temperature stage, a vacuum oven is used;

- the change of stages is accompanied by thermal shock, which provides relaxation of the accumulated intergrain mechanical stresses in the places of their conjugation in the system "bunch - inorganic filler";

- the controlled yield of decomposition products of the temporary binder and the rate of shrinkage provide consistent maintenance of temperature and residual pressure in the vacuum chamber by known methods at all stages of removal of the temporary binder;

- the preservation of the achieved qualitative results is ensured through the use in a temporary binder of a combination of functionally dispersed components: a dispersant and a lubricant additive.

The dispersant (surfactant) is two-component:

- beeswax, which in the process of removing the binder is condensed and returned to production;

- vinyl acetate, the decomposition products of which are pumped out by a vacuum pump.

The two-component lubricant additive provides the performance of its fluidizing functions in a wide temperature range:

- petrolatum oil with an alkane chain length (from C ₁₁ to C ₁₄ );

- paraffin with an alkane chain length (from C ₂₀ to C ₃₀ ).

Paraffin components, which are separately condensed in the binder removal step, are returned to production.

Coordinated isothermal and isobaric extracts provide optimization of the product shrinkage rate and the removal of temporary binder.

A mixture of powders is used as the initial inorganic filler, in which the main phase is tungsten carbide, the phases are tantalum carbide, chromium carbide, vanadium carbide, and cobalt powder acts as a permanent binder. The ratio of components determines the final properties of the hard alloy and its possible applications.

The method of the present invention is illustrated by examples of specific performance.

Example 1

1.1. Preparation of a binder for a mixture of inorganic powder material. 2 g of beeswax, 3 g of sivilene (commercial name ethylene vinyl acetate) are mixed with 0.4 g of liquid paraffin and 53 g of paraffin.

1.2. 100 g of cobalt powder of particle size distribution гран ₅₀ = 0.5 μm, 0.5 g of chromium carbide powder of particle size distribution ида ₅₀ = 0.5 μm, 0.5 g of vanadium carbide powder of particle size ⌀ ₅₀ = 0.5 μm are mixed , 20 g of tantalum carbide powder of particle size distribution ⌀ ₅₀ = 0.5 μm and 880 g of tungsten carbide powder of particle size distribution ул ₅₀ = 0.5 μm.

1.3. Preparation of the mass for the shaping of the part.

58.4 g of a liquid temporary binder are mixed with 1001 g of an inorganic powder mixture until a uniform plastic state of the system with a temperature in the range from 100 to 120 ° C.

1.4. Giving geometrical shape to products by known methods and stabilizing its shape at room temperature, due to the effects of thixotropy (lubricant additive) and gelation (surface-active additive), respectively.

1.5. Preliminary low-temperature removal of a temporary ligament in a vacuum oven (first stage).

The products are loaded into a vacuum oven, the chamber is pumped out to a residual pressure of 13 Pa. Heated at a speed in the range of 10 degrees per hour, providing the above residual pressure in the chamber or, in other words, the rate of departure of the temporary ligament from the body of the product in the throttling mode. Isothermal extracts to ensure the above residual pressure correspond to temperatures of 50 and 120 ° C. The first stage to a temperature of 300 ° C was performed on standard equipment SPT-200.

1.6. High-temperature removal of temporary ligaments in a vacuum furnace (second stage).

Products are transferred from a vacuum thermostat to a vacuum oven, subjecting it to thermal shock to room temperature, which provides relaxation of the mechanical stress of the mismatch accumulated in the interface region of the phase boundaries. The chamber of the vacuum furnace is pumped out to a residual pressure of 1.3 Pa. Heated products at a speed of 20 degrees per hour to a temperature of 300 ° C and 180 degrees per hour to a temperature of 1370 ° C in the throttling mode to maintain a residual pressure of 0.13 Pa.

1.7. Sinter products at a temperature of 1370 ° C in an argon atmosphere at a pressure of 4.5 · 10 ⁶ PA. The second stage was carried out on standard START 1.31 equipment; vacuum compression sintering furnaces of the COD733RL type are suitable for this purpose.

Example 2

2.1. Preparation of a binder for a mixture of inorganic powder material. 8 g of beeswax, 9 g of sivilene (commercial name ethylene vinyl acetate) are mixed with 1 g of liquid paraffin and 60 g of paraffin.

2.2. Preparation of an inorganic powdery mixture of materials. 100 g of cobalt powder of particle size distribution ⌀ ₅₀ = 0.5 μm, 1.5 g of powder of chromium carbide powder of particle size distribution ⌀ ₅₀ = 0.5 μm, 1.5 g of vanadium carbide powder of particle size distribution ⌀ ₅₀ = 0.5 μm, 20 g of powder are mixed tantalum carbide particle size distribution ⌀ ₅₀ = 0.5 μm and 880 g of tungsten carbide powder particle size distribution ⌀ ₅₀ = 0.5 μm.

2.3. Preparation of the mass for the shaping of the part. 78 g of a liquid temporary binder are mixed with 1003 g of an inorganic powder mixture until a uniform plastic state of the system with a temperature in the range from 100 to 120 ° C.

2.4. Giving geometrical shape to products by known methods and stabilizing its shape at room temperature, due to the effects of thixotropy (lubricant additive) and gelation (surface-active additive), respectively.

2.5. Preliminary low-temperature removal of a temporary ligament in a vacuum oven (first stage).

The products are loaded into a vacuum oven, the chamber is pumped out to a residual pressure of 1.3 Pa. Heated at a speed of 20 degrees per hour, providing the above residual pressure in the chamber or, in other words, the rate of departure of the temporary ligament from the body of the product in the throttling mode. Isothermal extracts to ensure the above residual pressure correspond to temperatures of 50 and 120 ° C. The first stage to a temperature of 300 ° C was performed on standard equipment SPT-200.

2.6. High-temperature removal of temporary ligaments in a vacuum furnace (second stage).

Products are transferred from a vacuum thermostat to a vacuum oven, subjecting it to thermal shock to room temperature, which provides relaxation of the mechanical stress of the mismatch accumulated in the interface region of the phase boundaries. The chamber of the vacuum furnace is pumped out to a residual pressure of 0.13 Pa. Heated products at a speed of 30 degrees per hour to a temperature of 300 ° C and 180 degrees per hour to a temperature of 1390 ° C in the throttling mode to maintain a residual pressure of 0.13 Pa.

2.7. Sinter products at a temperature of 1390 ° C in an argon atmosphere at a pressure of 5.5 · 10 ⁶ PA. The second stage was carried out on standard START 1.31 equipment; vacuum compression sintering furnaces of the COD733RL type are suitable for this purpose.

Example 3

3.1. Preparation of a binder for a mixture of inorganic powder material.

2 g of beeswax, 2 g of sivilene (commercial name ethylene vinyl acetate) are mixed with 0.5 g of liquid paraffin and 52 g of paraffin.

3.2. 100 g of cobalt powder of particle size distribution гран ₅₀ = 0.5 μm, 0.5 g of powder of chromium carbide powder of particle size distribution ⌀ ₅₀ = 0.5 μm, 0.5 g of powder of vanadium carbide particle size distribution ⌀ ₅₀ = 0.5 μm and 900 g of powder are mixed tungsten carbide particle size distribution ⌀ ₅₀ = 0.5 μm.

3.3. Preparation of the mass for the shaping of the part.

Mix 56.5 g of a liquid temporary binder with 1001 g of inorganic powder mixture until a uniform plastic state of the system with a temperature in the range from 100 to 120 ° C.

3.4. Giving geometrical shape to products by known methods and stabilizing its shape at room temperature, due to the effects of thixotropy (lubricant additive) and gelation (surface-active additive), respectively.

3.5. Preliminary low-temperature removal of a temporary ligament in a vacuum oven (first stage).

The products are loaded into a vacuum oven, the chamber is pumped out to a residual pressure of 13 Pa. Heated at a speed of 10 degrees per hour, providing the above residual pressure in the chamber or, in other words, the rate of departure of the temporary ligament from the body of the product in the throttling mode. Isothermal extracts to ensure the above residual pressure correspond to temperatures of 50 and 120 ° C. The first stage to a temperature of 300 ° C was performed on standard equipment SPT-200.

3.6. High-temperature removal of temporary ligaments in a vacuum furnace (second stage). Products are transferred from a vacuum thermostat to a vacuum oven, subjecting it to thermal shock to room temperature, which provides relaxation of the mechanical stress of the mismatch accumulated in the interface region of the phase boundaries. The chamber of the vacuum furnace is pumped out to a residual pressure of 1.3 Pa. Heated products at a speed of 20 degrees per hour to a temperature of 300 ° C and 180 degrees per hour to a temperature of 1370 ° C in the throttling mode to maintain a residual pressure of 0.13 Pa.

3.7. Sinter products at a temperature of 1370 ° C in an argon atmosphere at a pressure of 4.5 · 10 ⁶ PA. The second stage was carried out on standard START 1.31 equipment; vacuum compression sintering furnaces of the COD733RL type are suitable for this purpose.

Example 4

4.1. Preparation of a binder for a mixture of inorganic powder material.

7 g of beeswax, 8 g of sivilene (commercial name ethylene vinyl acetate) are mixed with 1 g of liquid paraffin and 59 g of paraffin.

4.2. Preparation of an inorganic powdery mixture of materials.

100 g of cobalt powder of particle size distribution ⌀ ₅₀ = 0.5 μm, 1.5 g of powder of chromium carbide powder of particle size distribution ⌀ ₅₀ = 0.5 μm, 1.5 g of powder of vanadium carbide particle size distribution ⌀ ₅₀ = 0.5 μm and 900 g of powder are mixed tungsten carbide particle size distribution ⌀ ₅₀ = 0.5 μm.

4.3. Preparation of the mass for the shaping of the part.

75 g of a liquid temporary binder are mixed with 1003 g of an inorganic powder mixture until a uniform plastic state of the system with a temperature in the range from 100 to 120 ° C.

4.4. Giving geometrical shape to products by known methods and stabilizing its shape at room temperature, due to the effects of thixotropy (lubricant additive) and gelation (surface-active additive), respectively.

4.5. Preliminary low-temperature removal of a temporary ligament in a vacuum oven (first stage).

The products are loaded into a vacuum oven, the chamber is pumped out to a residual pressure of 1.3 Pa. Heated at a speed of 20 degrees per hour, providing the above residual pressure in the chamber or, in other words, the rate of departure of the temporary ligament from the body of the product in the throttling mode. Isothermal extracts to ensure the above residual pressure correspond to temperatures of 50 and 120 ° C. The first stage to a temperature of 300 ° C was performed on standard equipment SPT-200.

4.6. High-temperature removal of temporary ligaments in a vacuum furnace (second stage).

Products are transferred from a vacuum thermostat to a vacuum oven, subjecting it to thermal shock to room temperature, which provides relaxation of the mechanical stress of the mismatch accumulated in the interface region of the phase boundaries. The chamber of the vacuum furnace is pumped out to a residual pressure of 0.13 Pa. Heated products at a speed of 30 degrees per hour to a temperature of 300 ° C and 180 degrees per hour to a temperature of 1390 ° C in the throttling mode to maintain a residual pressure of 0.13 Pa.

4.7. Sinter products at a temperature of 1390 ° C in an argon atmosphere at a pressure of 5.5 · 10 ⁶ PA. The second stage was carried out on standard START 1.31 equipment; vacuum compression sintering furnaces of the COD733RL type are suitable for this purpose.

Comparative physico-chemical and mechanical characteristics of the quality of the products obtained are given in the table

The name of indicators Analogs Experiment T5K10 VK10 MC131 Example 1 Example 4 WC TaS With we Co WC TaS Co WC TaS With WC With Composition (% wt.) 85 6 9 90 10 85 5 10 88 2 10 90 10 Density (g / cm ³ ) 12.4-13.1 14.5 11.35-11.51 14.59 14.55 Durable outgoing (MPa) 1421 2800 1400 1780 1820 HRA (not less) 88.5 87.5 91 91 Hv ₁₀ 1200 Hv ₃₀ 1430-1570

(мкм) $\overline{\varnothing }$

(microns) 0.5 0.5 0.5 0.5 0.5

T.O. A method for manufacturing carbide products from powders of compounds of a number of carbides is proposed, including mixing with a binder, geometrical shaping of the part, thermal removal of the temporary binder and sintering of the part, while thermal removal of the temporary binder is carried out in two stages in a vacuum, with the residual pressure at the first stage and the temperature is maintained in the range from 13 to 1.3 Pa in the temperature range from room temperature to 300 ° C; in the second stage, in the range of values from 1.3 to 0.13 Pa in the temperature range from room temperature tnoj to 1350 ° C, then sintered item pressurized inert gas at temperatures ranging from 1370 to 1390 ° C. At a residual pressure of the products of decomposition of the temporary binder from 13 to 1.3 Pa and from 1.3 to 0.13 Pa at temperatures of 50 ° C and 120 ° C, isothermal exposure is performed until the residual pressure is stabilized in the above ranges. The product is sintered in an inert gas atmosphere under pressure from 4.5 · 10 ⁶ to 5.5 · 10 ⁶ Pa in the temperature range from 1370 to 1390 ° C.

Also provided is a binder composition for implementing the method, comprising a temporary binder and a constant for powder mixtures of the components of a number of carbides and consisting of a two-component dispersant and a two-component lubricant additive in a ratio (weight) from 1: 3.6 to 1: 13.1. The composition of the temporary ligament includes a two-component dispersant: beeswax and ethylene vinyl acetate in a ratio (weight) from 1: 1 to 1: 1.15; also a two-component lubricant additive: liquid paraffin (C ₁₁ to C ₁₄ ) and paraffin (C ₂₀ to C ₃₀ ) in a ratio of 1: 104 to 1: 132. As a constant bond, cobalt was used in the ratio (wt.) With inorganic materials of powders of chromium carbide, vanadium carbide, tantalum carbide and tungsten carbide, respectively, from 66.6: 1: 1: 13.3: 586.6 to 200: 1: 1: 40: 1760 of one particle size distribution composition from 0.5 to 1.0 microns. As a constant bond, cobalt was used in the ratio (wt.) With inorganic materials of powders of chromium carbide, vanadium carbide, and tungsten carbide, respectively, from 66: 1: 1: 600 to 200: 1: 1: 1800 of one particle size distribution from 0.5 to 1.0 μm. The ratio (wt.) Of the temporary binder and the powder mixture of inorganic components before shaping is, respectively, from 1: 12.8 to 1: 17.7.

This application shows the quality indicators of the proposed technical solution, its practical applicability, inventive step, novelty.

Claims (9)

1. A method of manufacturing powder products from carbides based on hard alloys, comprising mixing a temporary binder and a powder mixture of inorganic powders, containing carbide powders and a permanent binder, forming a part, thermal removal of a temporary binder and sintering of a part, characterized in that they use a temporary binder containing a two-component dispersant and a two-component lubricant additive in a weight ratio of 1: 3.6 to 1: 13.1, with thermal removal of the temporary binder lead in two stages in a vacuum, and in the first stage, the residual pressure is maintained in the range from 13 to 1.3 Pa when heated from room temperature to 300 ° C, in the second stage in the range from 1.3 to 0.13 Pa at heating from room temperature to 1370 ° C or 1390 ° C, and sintering is carried out under overpressure of an inert gas in the temperature range from 1370 to 1390 ° C. 2. The method according to claim 1, characterized in that at a residual pressure of the decomposition products of the temporary binder from 13 to 1.3 Pa and from 1.3 to 0.13 Pa at isothermal temperatures of 50 ° C and 120 ° C, isothermal exposure residual pressure. 3. The method according to claim 1, characterized in that the product is sintered in an inert gas atmosphere under a pressure of from 4.5 · 10 ⁶ to 5.5 · 10 ⁶ PA. 4. The method according to claim 1, characterized in that cobalt powder is used as a permanent binder, and chromium carbide, vanadium carbide, tantalum carbide and tungsten carbide powders are used as carbides in the following weight ratio of components, respectively, from 66.6: 1: 1: 13.3: 586.6 to 200: 1: 1: 40: 1760, while the powders used have the same particle size distribution from 0.5 to 1.0 microns. 5. The method according to claim 1, characterized in that cobalt powder is used as a permanent binder, and chromium carbide, vanadium carbide and tungsten carbide powders are used as carbides in the following weight ratio of components, respectively, from 66: 1: 1: 600 to 200 : 1: 1: 1800 while the powders used have the same particle size distribution from 0.5 to 1.0 microns. 6. The method according to claim 1, characterized in that the weight ratio of the temporary binder and a powder mixture of inorganic components before the formation of the part is, respectively, from 1: 12.8 to 1: 17.7. 7. A temporary binder for forming a part in the manufacture of carbide-based hard alloy powder products by the method according to any one of claims 1 to 6, comprising a two-component dispersant and a two-component lubricant additive in a weight ratio of from 1: 3.6 to 1: 13.1. 8. The temporary binder according to claim 7, characterized in that as a two-component dispersant, it contains beeswax and ethylene vinyl acetate in a weight ratio of from 1: 1 to 1: 1.15. 9. The temporary binder according to claim 7, characterized in that, as a two-component lubricating additive, it contains liquid paraffin (C ₁₁ to C ₁₄ ) and paraffin (C ₂₀ to C ₃₀ ) in a weight ratio of 1: 104 to 1: 132.