CN111793773B

CN111793773B - High-speed steel through Laves phase and mu phase composite strong hardening and preparation method thereof

Info

Publication number: CN111793773B
Application number: CN201910734891.6A
Authority: CN
Inventors: 康希越; 谢丰伟; 袁紫仁; 贺跃辉
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2019-08-09
Filing date: 2019-08-09
Publication date: 2021-10-12
Anticipated expiration: 2039-08-09
Also published as: CN111793773A

Abstract

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 thereof₂Nb，Fe₂Ti，Fe₂W, the mu phase contains Fe₇Mo₆，Co₇Mo₆，Fe₇W₆，Co₇W₆. 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.

Description

High-speed steel through Laves phase and mu phase composite strong hardening and preparation method thereof

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.

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.

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/cm²Break off ofThe toughness is 20-35 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 0.6wt% 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-sized Laves phase provides high hardness and wear resistance, and compared with single-phase micro-phase intermetallic compound strongly hardened high-speed steel, the Laves phase is goldThe introduction of the intergeneric compound can obviously improve the hardness and the 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

Example 1

According to the design schemeThe formula comprises the following raw materials in percentage by mass: fe: 50%, Co: 20%, Mo: 15%, W: 8%, Nb: 3%, Ti:3 percent. Putting the raw material powder, 0.5 wt% of carbon black and 3 wt% of forming agent paraffin into a roller ball mill in nitrogen atmosphere for wet ball milling, wherein the ball milling medium is alcohol, the ball-material ratio is 6:1, and the ball milling time is 48 h. And drying and screening the mixed raw materials subjected to ball milling to prepare particles, and performing two-way die pressing with the pressing pressure of 200MPa to obtain a cold pressed blank. And sintering the obtained pressed compact in a vacuum sintering furnace at the maximum sintering temperature of 1380 ℃, and cooling to obtain a sintered compact. And (3) carrying out solid solution treatment on the sintered blank in a salt bath, and carrying out oil cooling, wherein the solid solution temperature is 1270 ℃, and the solid solution time is 12 min. The hardness of the material in a solid solution state was HRC 42.7. And (3) aging the solid-solution-state material in the air atmosphere of a box furnace at the aging temperature of 620 ℃ for 1h to obtain a finished product of the high-speed steel material with multiple intermetallic compound phases compounded and strongly hardened. The hardness of the material is HRC69.0, the bending strength is 2430MPa, and the impact toughness is 6.9J/cm²The fracture toughness is 23.3 MPa.m^1/2The hardness after heat preservation for 3 hours at 700 ℃ is HRC 61.7.

Example 2

The raw materials are prepared according to a design scheme formula, and the mass percentage is as follows: fe: 56%, Co: 20%, Mo: 13%, W: 5%, Nb: 4%, Ti: 2 percent. Putting the raw material powder, 0.5 wt% of carbon black and 3 wt% of forming agent paraffin into a roller ball mill in nitrogen atmosphere for wet ball milling, wherein the ball milling medium is alcohol, the ball-material ratio is 6:1, and the ball milling time is 50 h. And drying and screening the mixed raw materials subjected to ball milling to prepare particles, and performing bidirectional die pressing with the pressing pressure of 180MPa to obtain a cold pressed blank. And sintering the obtained pressed compact in a vacuum sintering furnace at the maximum sintering temperature of 1340 ℃, and cooling to obtain a sintered compact. And (3) carrying out solid solution treatment on the sintered blank in a salt bath, and carrying out oil cooling, wherein the solid solution temperature is 1260 ℃, the solid solution time is 15min, and the hardness of the solid solution material is HRC 42.3. And (3) aging the solid-solution-state material in the air atmosphere of a box furnace at the aging temperature of 620 ℃ for 1h to obtain a finished product of the high-speed steel material with multiple intermetallic compound phases compounded and strongly hardened. The hardness of the material is HRC68.7, and the bending resistance is strongThe degree is 2520MPa, and the impact toughness is 7.3J/cm²The fracture toughness is 25.7 MPa.m^1/2The hardness is HRC61.3 after heat preservation for 3 hours at 700 ℃.

Example 3

The raw materials are prepared according to a design scheme formula, and the mass percentage is as follows: fe: 56%, Co: 18%, Mo: 12%, W: 4%, Nb: 2%, Ti: 2 percent. Putting the raw material powder, 0.6wt% of carbon black and 4 wt% of forming agent paraffin into a roller ball mill in nitrogen atmosphere for wet ball milling, wherein the ball milling medium is alcohol, the ball-material ratio is 5:1, and the ball milling time is 50 h. And drying and screening the mixed raw materials subjected to ball milling to prepare particles, and performing bidirectional die pressing with the pressing pressure of 180MPa to obtain a cold pressed blank. And sintering the obtained pressed blank in a vacuum sintering furnace at the maximum sintering temperature of 1330 ℃, and cooling to obtain the sintered blank. And (3) carrying out solid solution treatment on the sintered blank in a salt bath, and carrying out oil cooling, wherein the solid solution temperature is 1260 ℃, and the solid solution time is 15 min. The hardness of the material in a solid solution state was HRC 42.2. And (3) aging the solid-solution-state material in the air atmosphere of a box furnace at the aging temperature of 620 ℃ for 1h to obtain a finished product of the high-speed steel material with multiple intermetallic compound phases compounded and strongly hardened. The hardness of the material is HRC68.1, the bending strength is 2960MPa, and the impact toughness is 9.8J/cm²The fracture toughness is 31.4 MPa.m^1/2The hardness is HRC60.5 after heat preservation for 3 hours at 700 ℃.

Example 4

The raw materials are prepared according to a design scheme formula, and the mass percentage is as follows: fe: 59%, Co: 20%, Mo: 15%, W: 3%, Nb: 3 percent and 0 percent of Ti. Putting the raw material powder, 0.5 wt% of carbon black and 3 wt% of forming agent paraffin into a roller ball mill in nitrogen atmosphere for wet ball milling, wherein the ball milling medium is alcohol, the ball-material ratio is 6:1, and the ball milling time is 48 h. And drying and screening the mixed raw materials subjected to ball milling to prepare particles, and performing two-way die pressing with the pressing pressure of 200MPa to obtain a cold pressed blank. And sintering the obtained pressed blank in a vacuum sintering furnace, wherein the maximum sintering temperature is 1350 ℃, and cooling to obtain a sintered blank. Carrying out solid solution treatment on the sintered blank in salt bath and carrying out oil cooling, wherein the solid solution temperature is 1250 ℃, the solid solution time is 12min, and the solid solution state materialThe hardness was HRC 41.9. And (3) aging the solid-solution-state material in the air atmosphere of a box furnace at the aging temperature of 620 ℃ for 1h to obtain a finished product of the high-speed steel material with multiple intermetallic compound phases compounded and strongly hardened. The hardness of the material is HRC68.4, the bending strength is 3020MPa, and the impact toughness is 10.3J/cm²The fracture toughness is 28.3 MPa.m^1/2The hardness is HRC60.9 after heat preservation for 3 hours at 700 ℃.

Example 5

The raw materials are prepared according to a design scheme formula, and the mass percentage is as follows: fe: 59%, Co: 20%, Mo: 15%, W: 3%, Nb: 0% and 3% of Ti. Putting the raw material powder, 0.5 wt% of carbon black and 3 wt% of forming agent paraffin into a roller ball mill in nitrogen atmosphere for wet ball milling, wherein the ball milling medium is alcohol, the ball-material ratio is 6:1, and the ball milling time is 48 h. And drying and screening the mixed raw materials subjected to ball milling to prepare particles, and performing two-way die pressing with the pressing pressure of 200MPa to obtain a cold pressed blank. And sintering the obtained pressed blank in a vacuum sintering furnace, wherein the maximum sintering temperature is 1350 ℃, and cooling to obtain a sintered blank. And (3) carrying out solid solution treatment on the sintered blank in a salt bath, and carrying out oil cooling, wherein the solid solution temperature is 1250 ℃, the solid solution time is 12min, and the hardness of the solid solution material is HRC 41.8. And (3) aging the solid-solution-state material in the air atmosphere of a box furnace at the aging temperature of 620 ℃ for 1h to obtain a finished product of the high-speed steel material with multiple intermetallic compound phases compounded and strongly hardened. The hardness of the material is HRC68.3, the bending strength is 2980MPa, and the impact toughness is 9.7J/cm²The fracture toughness is 27.7 MPa.m^1/2The hardness is HRC60.8 after heat preservation for 3 hours at 700 ℃.

Comparative example 1

The raw materials are prepared according to the formula, and the mass percentage is as follows: fe: 37%, Co: 25%, Mo: 20%, W: 8%, Nb: 5 percent and 5 percent of Ti. Putting the raw material powder, 0.5 wt% of carbon black and 3 wt% of forming agent paraffin into a roller ball mill in nitrogen atmosphere for wet ball milling, wherein the ball milling medium is alcohol, the ball-material ratio is 6:1, and the ball milling time is 48 h. And drying and screening the mixed raw materials subjected to ball milling to prepare particles, and performing two-way die pressing with the pressing pressure of 200MPa to obtain a cold pressed blank. The obtained green compact is put inSintering in an air sintering furnace, wherein the maximum sintering temperature is 1360 ℃, and cooling to obtain a sintered blank. And (3) carrying out solid solution treatment on the sintered blank in a salt bath, and carrying out oil cooling, wherein the solid solution temperature is 1270 ℃, the solid solution time is 12min, and the hardness of the solid solution material is HRC 45.8. And (3) aging the solid-solution-state material in the air atmosphere of a box furnace at the aging temperature of 610 ℃ for 1h to obtain a finished product of the high-speed steel material with strong hardening of the composite phase of various intermetallic compounds. The hardness of the material is HRC69.1, the bending strength is 2060MPa, and the impact toughness is 5.9J/cm²And a fracture toughness of 19.7MPa · m^1/2The hardness is HRC62.0 after heat preservation for 3 hours at 700 ℃.

Comparative example 2

The raw materials are prepared according to the formula, and the mass percentage is as follows: fe: 65%, Co: 20%, Mo: 10%, W: 5%, Nb: 0% and Ti 0%. Putting the raw material powder, 0.5 wt% of carbon black and 3 wt% of forming agent paraffin into a roller ball mill in nitrogen atmosphere for wet ball milling, wherein the ball milling medium is alcohol, the ball-material ratio is 6:1, and the ball milling time is 48 h. And drying and screening the mixed raw materials subjected to ball milling to prepare particles, and performing two-way die pressing with the pressing pressure of 200MPa to obtain a cold pressed blank. And sintering the obtained pressed blank in a vacuum sintering furnace, wherein the maximum sintering temperature is 1350 ℃, and cooling to obtain a sintered blank. And (3) carrying out solid solution treatment on the sintered blank in a salt bath, and carrying out oil cooling, wherein the solid solution temperature is 1240 ℃, the solid solution time is 12min, and the hardness of the solid solution material is HRC 40.1. And (3) aging the solid-solution-state material in the air atmosphere of a box furnace at the aging temperature of 620 ℃ for 1h to obtain a finished product of the high-speed steel material with multiple intermetallic compound phases compounded and strongly hardened. The hardness of the material is HRC64.4, the bending strength is 2980MPa, and the impact toughness is 9.8J/cm²The fracture toughness is 34.2 MPa.m^1/2，The hardness is HRC58.4 after heat preservation for 3 hours at 700 ℃.

Comparative example 3

The raw materials are prepared according to a design scheme formula, and the mass percentage is as follows: fe: 25%, Co: 30%, Mo: 30%, W: 5%, Nb: 5%, Ti:5 percent. Putting raw material powder, 0.6wt% of carbon black and 4 wt% of forming agent paraffin into a roller ball mill in nitrogen atmosphere for wet grindingBall milling is carried out, the ball milling medium is alcohol, the ball-material ratio is 6:1, and the ball milling time is 48 hours. And drying and screening the mixed raw materials subjected to ball milling to prepare particles, and performing bidirectional die pressing with the pressing pressure of 180MPa to obtain a cold pressed blank. And sintering the obtained pressed blank in a vacuum sintering furnace, wherein the maximum sintering temperature is 1350 ℃, and cooling to obtain a sintered blank. And (3) carrying out solid solution treatment on the sintered blank in a salt bath, and carrying out oil cooling, wherein the solid solution temperature is 1240 ℃, and the solid solution time is 15 min. The hardness of the material in a solid solution state is HRC 48.5. And (3) aging the solid-solution-state material in the air atmosphere of a box furnace at the aging temperature of 610 ℃ for 1h to obtain a finished product of the high-speed steel material with strong hardening of the composite phase of various intermetallic compounds. The hardness of the material is HRC69.1, the bending strength is 1750MPa, and the impact toughness is 3.2J/cm²The fracture toughness is 18.2 MPa.m^1/2The hardness is HRC62.5 after heat preservation for 3 hours at 700 ℃.

Comparative example 4

The raw materials are prepared according to a design scheme formula, and the mass percentage is as follows: fe: 51%, Co: 22%, Mo: 15%, W: 6%, Nb: 3%, Ti:3 percent. Putting the raw material powder, 0.5 wt% of carbon black and 3 wt% of forming agent paraffin into a roller ball mill in nitrogen atmosphere for wet ball milling, wherein the ball milling medium is alcohol, the ball-material ratio is 6:1, and the ball milling time is 60 hours. And drying and screening the mixed raw materials subjected to ball milling to prepare particles, and performing bidirectional die pressing with the pressing pressure of 180MPa to obtain a cold pressed blank. And sintering the obtained pressed blank in a vacuum sintering furnace at the maximum sintering temperature of 1250 ℃, and cooling to obtain the sintered blank. And (3) carrying out solid solution treatment on the sintered blank in a salt bath, and carrying out oil cooling, wherein the solid solution temperature is 1230 ℃, and the solid solution time is 15 min. The hardness of the material in a solid solution state is HRC 38.7. And (3) aging the solid-solution-state material in the air atmosphere of a box furnace at the aging temperature of 620 ℃ for 1h to obtain a finished product of the high-speed steel material with multiple intermetallic compound phases compounded and strongly hardened. The hardness of the material is HRC63.7, the bending strength is 1680MPa, and the impact toughness is 2.8J/cm²The fracture toughness is 16.8 MPa.m^1/2The hardness after heat preservation for 3 hours at 700 ℃ is HRC 59.2.

Comparative example 5

The raw materials are prepared according to a design scheme formula, and the mass percentage is as follows: fe: 56%, Co: 20%, Mo: 12%, W: 5%, Nb: 3%, Ti:3 percent. Putting the raw material powder, 0.5 wt% of carbon black and 3 wt% of forming agent paraffin into a roller ball mill in nitrogen atmosphere for wet ball milling, wherein the ball milling medium is alcohol, the ball-material ratio is 6:1, and the ball milling time is 55 h. And drying and screening the mixed raw materials subjected to ball milling to prepare particles, and performing bidirectional die pressing with the pressing pressure of 170MPa to obtain a cold pressed blank. And sintering the obtained pressed blank in a vacuum sintering furnace, wherein the maximum sintering temperature is 1360 ℃, and cooling to obtain the sintered blank. And (3) carrying out solid solution treatment on the sintered blank in a salt bath, and carrying out oil cooling, wherein the solid solution temperature is 1150 ℃ and the solid solution time is 12 min. The hardness of the material in a solid solution state is HRC 48.7. And (3) aging the solid-solution-state material in the air atmosphere of a box furnace at the aging temperature of 610 ℃ for 1h to obtain a finished product of the high-speed steel material with strong hardening of the composite phase of various intermetallic compounds. The hardness of the material is HRC64.2, the bending strength is 2110MPa, and the impact toughness is 5.4J/cm²The fracture toughness is 18.3 MPa.m^1/2The hardness after heat preservation for 3 hours at 700 ℃ is HRC 59.7.

Compared with the performance of the comparative example, the novel powder metallurgy high-speed steel which is prepared by the technical route and is strongly hardened by compounding the Laves phase intermetallic compound and the mu phase intermetallic compound has high bending strength and impact toughness and high-temperature red hardness which is far higher than that of carbide high-speed steel compared with the carbide high-speed steel; the alloy has more excellent toughness than the hard alloy. The novel Laves phase and mu phase intermetallic compound phase composite strong-hardening powder metallurgy high-speed steel prepared by the method fills the application blank between high-speed steel and hard alloy, and is a novel powder metallurgy high-speed steel material with high application value.

TABLE 1 comparison of mechanical properties of powder metallurgy high-speed steel material and conventional tool material prepared in example

TABLE 2 results of performance test of powder metallurgy high-speed steel material prepared in comparative example

Claims

1. a preparation method of high-speed steel by Laves phase and μ phase composite strong hardening, is characterized in that: comprise the steps:

1) Prepare Fe source powder, Co powder, Mo powder, W powder, Nb powder, Ti powder according to the designed proportion, mix to obtain mixed powder, add molding agent and carbon black to the mixed powder, ball mill and press to obtain compact;

2) placing the compact obtained in step 1) in a vacuum atmosphere for sintering, and cooling to obtain a sintered compact; the vacuum degree of the vacuum atmosphere is 0.001~0.1Pa, the sintering temperature is 1300~1450°C, and the sintering time is 1~2h;

3) Perform solution treatment on the sintered blank obtained in step 2), and after cooling to room temperature, perform multiple aging treatments to obtain high-speed steel; the solution treatment is performed in a salt bath or in a vacuum, and the solution temperature is 1200~ 1280℃, the solution time is 10~30min, and the cooling method is oil cooling; the aging treatment is carried out in an air atmosphere, the aging temperature is 550~650℃, the single aging time is 1h, and the number of times is 1~3 times.

The high-speed steel is composed of a steel matrix and a strong hardening phase dispersed in the steel matrix, the strong hardening phase is composed of a Laves phase and a μ phase, the Laves phase contains Fe ₂ Nb, Fe ₂ Ti, and the μ phase contains Fe ₇ Mo ₆ , Co ₇ Mo ₆ , Fe ₇ W ₆ , Co ₇ W ₆ ;

The particle size of the Laves phase is 3-10 μm, the μ-phase particle size includes a micron-sized particle size and a nano-sized particle size, the micro-sized particle size is 0.8-3 μm, and the nano-sized particle size is less than or equal to 100 nm,

The high-speed steel includes the following elements: at least one of Nb and Ti, Fe, Co, Mo, and W; the weight percentages of each element in the high-speed steel are: Co: 10-30%, Mo: 5-30 %, W: 2~20%, Nb: 0~10%, Ti: 0~10%, the balance is Fe,

The sum of the mass percentages of Nb and Ti in the high-speed steel is 1% to 6%.

2 . The method for preparing a high-speed steel through Laves phase and μ phase composite strong hardening according to claim 1 , wherein the iron source powder is carbonyl iron powder. 3 .

3 . The method for preparing high-speed steel through Laves phase and μ phase composite strong hardening according to claim 1 , wherein in the step 1), the amount of carbon black added is 0.2 of the mass of the mixed powder. 4 . -0.6wt%; in the step 1), the molding agent is paraffin, and the addition amount is 3-5wt% of the mass of the mixed powder.

4. The method for preparing high-speed steel through Laves phase and μ phase composite strong hardening according to claim 1, characterized in that: the ball milling process is carried out in an inert atmosphere, and the ball-to-material ratio is (5~7) : 1, the ball milling time is 48~60h, when the planetary ball mill is used, the rotational speed is 200~250r/min; when the drum ball mill is used, the rotational speed is 80~100r/min; in the step 1), cold pressing is adopted. Bidirectional pressing, pressing pressure is 150~200 MPa.