阅读说明：本技术 一种通过Laves相及μ相复合强硬化的高速钢及其制备方法 (High-speed steel through Laves phase and mu phase composite strong hardening and preparation method thereof ) 是由 康希越 谢丰伟 袁紫仁 贺跃辉 于 2019-08-09 设计创作，主要内容包括：本发明公开了一种通过Laves相及μ相复合强硬化的高速钢及其制备方法,所述高速钢由钢基体以及分散于钢基体中的强硬化相组成,所述强硬化相由Laves相及μ相组成,所述Laves相包含Fe<Sub>2</Sub>Nb,Fe<Sub>2</Sub>Ti,Fe<Sub>2</Sub>W,所述μ相包含Fe<Sub>7</Sub>Mo<Sub>6</Sub>,Co<Sub>7</Sub>Mo<Sub>6</Sub>,Fe<Sub>7</Sub>W<Sub>6</Sub>,Co<Sub>7</Sub>W<Sub>6</Sub>。本发明中通过烧结过程原位生成的Laves相及μ相等进行强硬化,细小的μ相对基体进行强化,使其在高温下拥有更高的硬度,高硬度大颗粒的Laves相赋予了材料更高的耐磨性。原位生成的金属间化合物强化相与基体间有着良好的界面关系,并且在高温下扩散速度慢,故材料在添加大量合金元素达到高硬度同时仍然保持着较高的强韧性和导热系数,并且有着出色抗回火性、高温硬度及高温强度,相较于传统高速钢在高温高速切削中有着更出色的表现。(The invention discloses high-speed steel which is subjected to composite strong hardening through a Laves phase and a mu phase and a preparation method thereof 2 Nb，Fe 2 Ti，Fe 2 W, the mu phase contains Fe 7 Mo 6 ，Co 7 Mo 6 ，Fe 7 W 6 ，Co 7 W 6 . In the invention, the Laves phase and the mu phase generated in situ in the sintering process are strongly hardened, and the fine mu phase is strengthened relative to the matrix, so that the material has higher hardness at high temperature, and the Laves phase with high hardness and large particles endows the material with higher wear resistance. The intermetallic compound strengthening phase generated in situ has good interface relation with the matrix, and the diffusion speed is slow at high temperature, so that the material achieves high hardness by adding a large amount of alloy elements, still keeps higher obdurability and heat conductivity coefficient, has excellent tempering resistance, high-temperature hardness and high-temperature strength, and has more excellent performance in high-temperature and high-speed cutting compared with the traditional high-speed steel.)

1. A high-speed steel which is strongly hardened by compounding Laves phase and mu phase is characterized in that: the high-speed steel consists of a steel matrix and a strong hardening phase dispersed in the steel matrix, wherein the strong hardening phase consists of a Laves phase and a mu phase, and the Laves phase contains Fe₂Nb，Fe₂Ti, the mu phase contains Fe₇Mo₆，Co₇Mo₆，Fe₇W₆，Co₇W₆。

2. The high speed steel hardened by a Laves phase and μ phase composite hardening according to claim 1, wherein:

the particle size of the Laves phase is 3-10 mu m, the particle size of the mu phase comprises a micron particle size and a nanometer particle size, the micron particle size is 0.8-3 mu m, and the nanometer particle size is less than or equal to 100 nm.

3. A high speed steel through Laves phase and μ phase composite hardening according to claim 1 or 2, characterized in that: the high-speed steel is prepared by powder metallurgy, and the strong hardening phase is generated in situ in the preparation process.

4. A high speed steel through Laves phase and μ phase composite hardening according to claim 1 or 2, characterized in that: the high-speed steel contains the following elements: at least one of Nb and Ti, Fe, Co, Mo, W; the weight percentages of the elements in the high-speed steel are as follows: co: 10-30%, Mo: 5-30%, W: 2-20%, Nb: 0-10% of Ti, 0-10% of Ti and the balance of Fe.

5. The high-speed steel hardened by a Laves phase and mu phase composite according to claim 4, wherein: the sum of the mass percentages of Nb and Ti in the high-speed steel is 1 to 6 percent.

6. Method for producing a high speed steel through composite hardening of Laves and μ phase according to claims 1-5, characterized in that: the method comprises the following steps:

1) mixing Fe source powder, Co powder, Mo powder, W powder, Nb powder and Ti powder according to a designed ratio to obtain mixed powder, adding a forming agent and carbon black into the mixed powder, and performing ball milling and compression molding to obtain a green compact;

2) placing the pressed blank obtained in the step 1) in a vacuum atmosphere for sintering, and cooling to obtain a sintered blank;

3) carrying out solid solution treatment on the sintered blank obtained in the step 2), cooling to room temperature, and carrying out aging treatment for multiple times.

7. The method of manufacturing a high speed steel through Laves phase and μ phase composite hardening according to claim 6, wherein: the iron source powder is carbonyl iron powder.

8. The method of manufacturing a high speed steel through Laves phase and μ phase composite hardening according to claim 6, wherein: in the step 1), the adding amount of the carbon black is 0.2-0.6 wt% of the mass of the mixed powder; in the step 1), the forming agent is paraffin, and the adding amount of the forming agent is 3-5 wt% of the mass of the mixed powder.

9. The method of manufacturing a high speed steel through Laves phase and μ phase composite hardening according to claim 6, wherein: the ball milling process is carried out in an inert atmosphere, the ball-material ratio is (5-7): 1, and the ball milling time is 48-60 hours. When a planetary ball mill is used, the rotating speed is 200-250 r/min; when a roller ball mill is used, the rotating speed is 80-100 r/min; in the step 1), cold pressing bidirectional pressing is adopted, and the pressing pressure is 150-200 MPa.

10. The method of manufacturing a high speed steel through Laves phase and μ phase composite hardening according to claim 6, wherein: in the step 2), the vacuum degree of the vacuum atmosphere is 0.001-0.1 Pa, the sintering temperature is 1300-1450 ℃, and the sintering time is 1-2 h;

in the step 3), the solid solution treatment is carried out in a salt bath or vacuum, the solid solution temperature is 1200-1280 ℃, the solid solution time is 10-30 min, and the cooling mode is oil cooling;

in the step 3), the aging treatment is carried out in an air atmosphere, the aging temperature is 550-650 ℃, the single aging time is 1h, and the times are 1-3.

Technical Field

Since the last birth of the 19 th century, high-speed steel is one of the common cutter materials, and still accounts for 45 percent of the worldwide cutter sales share, has good red hardness and wear resistance which are not possessed by conventional carbon tool steel and alloy tool steel, and has shock resistance and heat treatment adjusting material mechanical property and machinability which are not possessed by hard alloy and ceramic cutters. However, with the continuous advance of industrialization, the traditional carbide hard-strengthened high-speed steel cannot completely meet the increasingly severe processing requirements, and the cost and resources consumed in the processing stage are a part which is not negligible.

Stainless steel, titanium alloy, high temperature alloy and other materials with poor processability are widely applied to various fields such as civil equipment, military equipment, chemical metallurgy, energy and power, automobile manufacturing and the like, and the use amount is increased year by year. But the machining difficulty is high, the machining efficiency is low, a large amount of heat generated in the cutting process cannot be conducted due to a low heat conductivity coefficient, and the cutting temperature is high; meanwhile, the surface of the part has an oxidation hardening area, so that the part has a strong abrasion effect on the cutter; and the chemical activity is high, the cutting tool is seriously stuck in the cutting process, accumulated chips are easily generated, and surface materials or coatings are taken away. At present, the traditional carbide high-hardening high-speed steel can not meet the processing requirements of the difficult-to-process materials. Because in conventional high speed steels, the aim of strengthening the material is usually achieved by the addition of carbides, the hardness is increased while the toughness is maintained high. However, because the carbide hard hardening phase is added, the matrix and the hardening phase have lower binding force and phase interface relationship, and the traditional carbide hard high-speed steel has lower heat conductivity coefficient, high-temperature hardness and strength. Under the severe high-temperature working condition of processing stainless steel, titanium alloy, high-temperature alloy and the like, a carbide strong hardening phase rapidly grows up, so that the strengthening effect is reduced, and the high-temperature hardness and the strength are rapidly reduced; meanwhile, the existence of carbon can aggravate the condition of tool sticking of the processed material and the high-speed steel tool, and serious diffusion abrasion is generated. These factors result in the plastic deformation of the tip of conventional carbide hardened high speed steels during machining, which fails to maintain sharpness and wears rapidly.

When these materials are machined, there are problems such as low efficiency of the machining process, low surface finish, large tool consumption, etc., and a large amount of resources are consumed. Aiming at the processing characteristics of titanium alloy and high-temperature alloy, the cutting tool must be made of a tool material with good red hardness, high strength and toughness, large heat conductivity coefficient, bonding resistance, diffusion resistance and excellent oxidation resistance.

Background

The invention belongs to the technical field of high-speed steel manufacturing, relates to high-hardness and high-toughness powder metallurgy high-speed steel, and particularly relates to high-speed steel through Laves phase and mu phase composite strong hardening and a preparation method thereof.

Disclosure of Invention

Aiming at the problems of low hardness and non-wear resistance of the traditional carbide high-hardness high-speed steel at high temperature and high speed in the prior art, the invention aims to provide the high-speed steel which has high hardness, high toughness and good wear resistance and is formed by in-situ generation of Laves phase and mu phase composite strong hardening and the preparation method thereof. In the invention, a plurality of intermetallic compound Laves phases and mu phases generated in situ in the sintering process are strongly hardened, and the fine mu phase is strengthened relative to the matrix, so that the matrix has higher hardness at high temperature, and the Laves phase with high hardness and large particles endows the material with higher wear resistance. The intermetallic compound strengthening phase generated in situ has good interface relation with the matrix, and the diffusion speed is slow at high temperature, so that the material achieves high hardness by adding a large amount of alloy elements, still keeps higher obdurability and heat conductivity coefficient, has excellent tempering resistance, high-temperature hardness and high-temperature strength, and has more excellent performance in high-temperature and high-speed cutting compared with the traditional high-speed steel.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention relates to high-speed steel which is subjected to composite strong hardening through a Laves phase and a mu phase, wherein the high-speed steel consists of a steel matrix and a strong hardening phase dispersed in the steel matrix, the strong hardening phase consists of the Laves phase and the mu phase, and the Laves phase contains Fe₂Nb，Fe₂Ti, the mu phase contains Fe₇Mo₆，Co₇Mo₆，Fe₇W₆，Co₇W₆。

In a preferable scheme, the particle size of the Laves phase is 3-10 μm, the particle size of the μ phase comprises a micron particle size and a nanometer particle size, the micron particle size is 0.8-3 μm, and the nanometer particle size is less than or equal to 100 nm.

According to the technical scheme, the particle size of the Laves phase is micron-sized, so that high-hardness particles are provided for the material, and the wear resistance and the high-temperature hardness of the material are ensured. The existence of the mu phase comprises micron and nanometer, the strengthening and hardening effects of the nanometer mu phase are obvious, the strength and hardness of the material matrix can be effectively and obviously improved, great contribution is made to the strength and hardness of the material, and the micron mu phase has the effect similar to that of Laves phase and is mainly used for improving the wear resistance.

Preferably, the high-speed steel is prepared by powder metallurgy, and the strong hardening phase is generated in situ in the preparation process.

Preferably, the high-speed steel contains the following elements: at least one of Nb and Ti, Fe, Co, Mo, W; the weight percentages of the elements in the high-speed steel are as follows: co: 10-30%, Mo: 5-30%, W: 2-20%, Nb: 0-10% of Ti, 0-10% of Ti and the balance of Fe.

More preferably, the sum of the mass percentages of Nb and Ti in the high-speed steel is 1 to 6 percent.

In the invention, the added Nb and Ti are important constituent elements for forming the Laves phase, however, the addition of too much Nb and Ti can cause the number of the Laves phase to be too large, and the toughness of the material is obviously reduced. Of course, the addition amount of other metals participating in the formation of the mu phase needs to be controlled properly, for example, W, if the addition amount is too large, the mu phase is formed too much, and the toughness of the high-speed steel is reduced.

In the preferable scheme, the weight percentages of the elements in the high-speed steel are as follows: co: 13-25%, Mo: 8-25%, W: 2-10%, Nb: 0-6% of Ti, 0-6% of Ti and the balance of Fe.

As a further preference, the weight percentages of the elements in the high-speed steel are as follows: co: 15-25%, Mo: 12-22%, W: 3-8%, Nb: 0-5%, Ti 0-5%, and the balance Fe.

As a further preference, the weight percentages of the elements in the high-speed steel are as follows: co: 18-20%, Mo: 12-15%, W: 3-4%, Nb: 0-3%, Ti 0-3%, and the balance Fe.

Preferably, the high-speed steel has the hardness of HRC 62-69, the bending strength of 2300-3100 MPa and the impact toughness of 6-11J/cm²The fracture toughness is 20 to 35 MPa.m^1/2The hardness of the alloy still keeps more than HRC58 after the alloy is kept for 3 hours at 700 ℃.

More preferably, the high-speed steel has a hardness of HRC 67-69, a bending strength of 2400-3100 MPa, and an impact toughness of 6.8-11J/cm²The fracture toughness is 22 to 35 MPa.m^1/2The hardness of the alloy still keeps more than HRC60 after the alloy is kept for 3 hours at 700 ℃.

The invention relates to a preparation method of high-speed steel through Laves phase and mu phase composite strong hardening, which comprises the following steps:

1) mixing Fe source powder, Co powder, Mo powder, W powder, Nb powder and Ti powder according to a designed ratio to obtain mixed powder, adding a forming agent and carbon black into the mixed powder, and performing ball milling and compression molding to obtain a green compact;

2) placing the pressed blank obtained in the step 1) in a vacuum atmosphere for sintering, and cooling to obtain a sintered blank;

3) carrying out solid solution treatment on the sintered blank obtained in the step 2), cooling to room temperature, and carrying out aging treatment for multiple times. In practice, the ageing treatment is carried out in an electric resistance furnace.

More preferably, the iron source powder is carbonyl iron powder.

The inventor finds that when carbonyl iron powder is adopted as the iron source powder, the smaller particle size and higher activity of the carbonyl iron powder can have the effect of promoting densification in sintering, so that the obtained high-speed steel has better compactness.

The starting powders used in the present invention are commercially high purity (> 99.8%) and ultrafine (average particle size < 8 μm) powders.

Preferably, in the step 1), the carbon black is added in an amount of 0.2 to 0.6 wt% based on the mass of the mixed powder.

Preferably, in the step 1), the forming agent is paraffin, and the adding amount is 3-5 wt% of the mixed powder.

Preferably, in the step 1), the ball milling equipment may be ball milling equipment in the prior art, such as a planetary ball mill or a roller ball mill. The ball milling process is carried out in an inert atmosphere, the ball-material ratio is (5-7): 1, and the ball milling time is 48-60 hours. When a planetary ball mill is used, the rotating speed is 200-250 r/min; when the roller ball mill is used, the rotating speed is 80-100 r/min.

In the preferable scheme, in the step 1), cold pressing bidirectional pressing is adopted, and the pressing pressure is 150-200 MPa.

In the preferable scheme, in the step 2), the vacuum degree of the vacuum atmosphere is 0.001-0.1 Pa, the sintering temperature is 1300-1450 ℃, and the sintering time is 1-2 h.

In the preferable scheme, in the step 3), the solid solution treatment is carried out in a salt bath or vacuum, the solid solution temperature is 1200-1280 ℃, the solid solution time is 10-30 min, and the cooling mode is oil cooling.

In the preferable scheme, in the step 3), the aging treatment is carried out in an air atmosphere, the aging temperature is 550-650 ℃, the single aging time is 1h, and the times are 1-3.

In the technical scheme of the invention, the raw material component proportion relation of the high-speed steel is the basis for forming the Laves phase and the mu phase in the required proportion, and the Laves phase and the mu phase are really controlled to form, distribute and proportion and need to be cooperated with the process phase, namely two intermetallic compound phases of the mu phase and the Laves phase are generated in situ by the heat preservation of metal element powder reaction at the corresponding phase zone temperature in the sintering process. Finally, the distribution and proportion of the Laves phase and the mu phase are adjusted through a heat treatment process. If the temperature is too high during sintering, other phases will be generated by entering other phase regions, and if too low, no μ phase will be generated and densification will not be achieved. The solid solution temperature is too low, and enough intermetallic compounds are not dissolved into the matrix, so that the aging effect is not obvious; too high a temperature may cause grain growth or ferrite transformation at high temperature, which may impair mechanical properties of the material. In addition, the aging temperature is too low to precipitate the mu phase, so that the Laves phase ratio is too high.

The high-speed steel with multiple intermetallic compound phases compounded and strongly hardened, which is prepared by the process of the invention, has the strengthening phase consisting of AB₂Form Laves phase and A₇B₆The micro-phase type micro-phase is composed of a fine micro-phase reinforced matrix, the micron-sized Laves phase provides high hardness and wear resistance, and compared with single-phase micro-phase intermetallic compound high-hardness high-speed steel, the introduction of the Laves phase intermetallic compound can obviously improve the hardness and high-temperature red hardness of the material.

The high-speed steel with the same hardness and toughness as the traditional carbide high-speed steel with the strong hardening effect also has the following advantages:

1. the material is strongly hardened through two intermetallic compounds simultaneously, so that the material has stronger tempering resistance and wear resistance, the diffusion activation energy of the intermetallic compound strengthening phase is far higher than that of carbide, the intermetallic compound strengthening phase has extremely strong aggregation resistance at high temperature of high-speed cutting, the aggregation growth rate of hard phases is greatly slowed down, and therefore, the high hardness can be kept at high temperature and far exceeds that of carbide high-speed steel with strong hardening.

2. The in-situ generated strengthening phase has good interface relation with the matrix phase, has high thermal conductivity (40-50W/(m.K) at 600 ℃) which is twice that of the traditional carbide high-speed steel (20-25W/(m.K) at 600 ℃), so the heat is easily transferred and the temperature is reduced during the cutting process, and the temperature of a tool nose is prevented from being too high.

3. More excellent by processing property, the material softens after high-temperature solution treatment, the hardness is HRC 40-45 by the processing property greatly increased, simultaneously, the aging hardening process has no deformation, the shape and the size of the cutter are stable, the deformation in the heat treatment process is avoided, and the preparation of parts with high precision and complex shapes is greatly facilitated.

4. The powder metallurgy method is adopted for preparation, the types and the contents of the added elements can be flexibly adjusted, the technical threshold of high gas atomization-hot isostatic pressing is avoided, the near-net forming is realized, the process flow is short, and the material utilization rate is high.

Drawings

FIG. 1 is a microstructure of a conventional powder metallurgy high speed steel

FIG. 2 shows the microstructure of the novel powder metallurgy high speed steel of example 1 prepared by the present patent technology

FIG. 3 shows the microstructure of the novel powder metallurgy high speed steel of example 5 prepared by the present technology

Detailed Description