A cemented carbide containing components of WC, Co, Ni, Cr, Al and a method for producing the same

Abstract

The application discloses a cemented carbide containing WC, Co, Ni, Cr and Al components and a preparation method thereof. The preparation method comprises the following steps: wet-mixing AlN powder with coarse WC powder, Co powder, Ni powder and Cr powder / Cr carbide, ball-milling until the point, then sequentially performing drying, screening, granulating, pressing into a green compact, then sequentially performing de-removal of a forming agent, solid-phase sintering, liquid-phase sintering and vacuum heat treatment. The application is designed and monitored according to the heating rate ΔT (0.2℃ / min~2.5℃ / min) of five different stages of the solid-phase sintering and the vacuum degree values P1~P5 (1.0Pa~20Pa) so as to judge whether the AlN cracking in the WC-Co-Ni-Cr-Al material is completed, to ensure that the alloy material enters the liquid-phase sintering after the solid-phase sintering is completed, and to ensure that no pore defects are generated in the alloy structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hard alloy, more particularly to a hard alloy containing WC, Co, Ni, Cr and Al components and a preparation method thereof. BACKGROUND

[0002] Hard alloy is mainly composed of refractory metal hard phase WC as matrix, Co or Ni as binder, and is a high-hardness and high-wear-resistance material prepared by powder metallurgy, which plays an irreplaceable role in cutting tool, impact tool and wear-resistant parts, and is one of the key hard materials indispensable to high-end manufacturing industry in China, and is given the title of "industrial tooth".

[0003] Hard alloy roller ring is also a composite material prepared by powder metallurgy with refractory metal compound as skeleton and transition metal as binder. Due to its high strength, high hardness, excellent wear resistance and high temperature resistance, it is widely used in the rolling production of bar, wire, special steel and threaded steel. Compared with traditional cast iron roller ring, the rolling efficiency of steel has been greatly improved.

[0004] Although the WC-Co hard alloy roller ring used in the early stage has good stability and reliability, its temperature when contacting red steel can be close to 80% of the liquid phase eutectic temperature. The latest generation of hard alloy roller rings for high-speed wire of foreign advanced enterprises generally use Co-Ni-Cr as binder, such as C10C, C15C, C20C, C25C and C30T roller ring grades of Sandvik Company in Sweden; the fourth generation SM-N series roller ring grades of SinterMet, LLC in the United States; and CE260 and other grades of CERAMETAL Company in Luxembourg. These roller ring grades of foreign advanced enterprises mainly add Ni and a small amount of Cr elements to improve the oxidation resistance and corrosion resistance of the binder phase, so that WC-Ni-Co-Cr has significantly higher wear resistance and high temperature oxidation resistance than WC-Co alloy under the condition of similar strength and hardness. The hard alloy roller ring using WC-Ni-Co-Cr material not only can improve the surface quality of rolled material, but also can improve the high temperature stability and corrosion resistance of the roller ring, and has a wider working condition range.

[0005]

[0006] ​WC-Co-Ni-Cr hard alloy has high hardness, strength and wear resistance, but in recent years with the downstream steel body enterprise technology innovation and progress, the traditional WC-Co-Ni-Cr hard alloy is difficult to adapt to the harsh working conditions of high stress and high strength. The state attaches great importance to the energy saving of steel industry, encourages the steel industry to introduce new technology. In 2018, the state implemented the new standard GB / T1499.2-2018 to replace GB / T1499.2-2007 for steel enterprises, and the rolling of threaded steel cannot obtain high strength by strong water cooling to avoid the generation of closed martensite structure; at the same time, in order to reduce the amount and cost of alloy elements, the most feasible method is to use low temperature rolling, that is, to carry out threaded steel rolling production below the recrystallization temperature, to avoid the grain growth of rolling deformation refinement, so as to reduce the content of alloy elements, improve the elongation and strength of the material, and will not produce closed martensite structure, meet the requirements of new national standard for steel performance and organizational structure.

[0007] With the progress of steel rolling technology and environmental protection cost control, steel enterprises increase the pace of improving product competitiveness and technological upgrading, and low temperature rolling technology is valued and applied by various enterprises. The application of WC-Co-Ni-Cr-Al material appears. The production and manufacture of WC-Co-Ni-Cr-Al material encounters certain difficulties. Although the addition of Al element promotes the improvement of mechanical properties of alloy material under high temperature conditions, elemental Al is easy to oxidize in the manufacturing process; in 1985, Japanese scholar Nishigaki proposed to use AlN instead of Al for addition in the 11th Plenary International Academic Conference, which generates γ' phase (Ni, Co)3Al in the sintering process, so that the alloy has excellent toughness, wear resistance, high temperature strength and oxidation resistance, which theoretically solves the problem.

[0008] Patent CN201110449684.X discloses a WC-Co-Ni-Al-B hard alloy roller ring material and a manufacturing method, which uses AlN instead of Al and adds trace B to improve the creep resistance, alloy strength, hardness and wear resistance of the hard alloy.

[0009] The related data literature reports that AlN is very stable at normal temperature and pressure, and WC-Co-Ni-Cr-Al hard alloy roller ring is produced by using AlN instead of Al. Because the product single weight is large (usually more than 10 kg), AlN will crack to different degrees in the sintering process, which will cause the appearance of Al oxide and induce the generation of porosity defects. This has a serious impact on the density of WC-Co-Ni-Cr-Al hard alloy roller ring product, and affects its mechanical properties. SUMMARY

[0010] The present application aims at the deficiencies and difficulties existing in the prior art, and provides a method for batch production of large single heavy coarse grain cemented carbide WC-Co-Ni-Cr-Al.

[0011] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0012] A cemented carbide containing WC, Co, Ni, Cr and Al components, in terms of mass percentage, comprising the following components: Co 7.5-16%, Ni 7.5-16%, Cr 0.5-1.0%, AlN 0.8-2.7%, and the balance being WC.

[0013] Preferably, the mass ratio of Co to Ni is 1:1.

[0014] Preferably, the particle size of the AlN powder is ≤2μm.

[0015] Another object of the present application is to provide a preparation method of the above-mentioned cemented carbide containing WC, Co, Ni, Cr and Al components, comprising: wet-mixing AlN powder with coarse WC powder, Co powder, Ni powder and Cr powder / Cr carbide, ball-milling to a point, then sequentially performing drying, sieving, granulating, pressing into a green compact, then sequentially performing binder removal, solid phase sintering, liquid phase sintering and vacuum heat treatment.

[0016] Preferably, the solid phase sintering comprises: the first stage 700-800℃ with a holding section, during which the vacuum is extracted to a limit of ≤5Pa, the second stage (700-800)℃-1000℃, the third stage 1000℃-1250℃, the fourth stage 1250℃-1290℃, and the fifth stage 1290℃-1320℃.

[0017] The vacuum degrees in the five solid phase sintering stages are monitored and named as P1, P2, P3, P4 and P5, respectively, wherein P1 takes the minimum value, and P2-P5 take the maximum value.

[0018] Take the minimum value of P1 as the basis for comparison, when P4≤P1, P4

[0019] If P4>P1, then adjust the heating rate of the fifth stage to achieve P5≤P1, then determine that the AlN cracking in the sintering process of WC-Co-Ni-Cr-Al material has been completed; if after adjustment, P5≤P1 cannot be achieved, then it is determined that the AlN cracking is not completed, and the alloy material after sintering may have porosity defects, which is a difficult to repair organizational defect, and the alloy material can only be scrapped.

[0020] AlN cracking is determined by two factors: temperature and vacuum degree. The smaller the vacuum degree value, the lower the cracking temperature, and vice versa. The temperature of cemented carbide solid phase sintering is generally not more than 1320℃-1350℃, and the AlN cracking is completed before the end of solid phase sintering. The smaller the vacuum degree value, the more conducive to completing the cracking at a lower temperature. The vacuum degree in the solid phase stage is dynamically changing, and the vacuum degree can be adjusted by adjusting the heating rate, but when the evaporation speed of the material exceeds the vacuum pumping limit of the sintering equipment, the vacuum degree value in P3 segment is very high, and the AlN cracking stops, while the vacuum system is still working. The residual AlN will continue to crack when the vacuum degree and temperature reach the conditions, which will cause P4≥P1.

[0021] When designing the solid phase sintering stage process, the heating rate of P3-P5 segment should be designed according to the actual vacuum pumping capacity P1 of the sintering equipment, to ensure that the vacuum cracking process of AlN is completed in P4 segment, and P5 segment is used as the finishing stage, taking into account the control of production cycle and cost.

[0022] Generally, the sintering process of cemented carbide is divided into three stages, namely, removal of forming agent, solid phase sintering and liquid phase sintering. The removal of forming agent is generally completed at 500-600 DEG C, and then the solid phase sintering is completed by heating to 1320-1350 DEG C, and then the liquid phase sintering is carried out at high temperature, and finally the cooling is carried out. In the WC-Co-Ni-Cr-Al material, the AlN cracking in the sintering process is mainly completed in the solid phase stage, which is also the key step for completing the sintering densification of the alloy material, that is, the control of the AlN cracking in the sintering process. If the uncracked residual AlN enters the liquid phase sintering stage, it may cause bubble porosity and Al oxide precipitation, affecting the densification of the alloy structure. Since the vacuum cracking of AlN can only occur under vacuum heating conditions, relevant papers have reported that AlN can be cracked at 800 DEG C or above under vacuum conditions. Therefore, the solid phase sintering stage of the WC-Co-Ni-Cr-Al product is designed as follows: the first stage is 700-800 DEG C, the second stage is 800-1000 DEG C, the third stage is 1000-1250 DEG C, the fourth stage is a verification stage of 1250-1290 DEG C, and the fifth stage is a finishing stage of 1290-1320 DEG C.

[0023] The temperature rising rate ΔT (0.2-2.5 DEG C / min) and the vacuum degree value P1-P5 (1.0-20 Pa) of the five different stages of the solid phase sintering of the WC-Co-Ni-Cr-Al material are designed and monitored, so as to determine whether the AlN cracking in the WC-Co-Ni-Cr-Al material is completed, and to ensure that the alloy material enters the liquid phase sintering after the solid phase sintering is completed.

[0024] Preferably, the fsss particle size of the coarse WC powder is greater than or equal to 20 microns.

[0025] Preferably, in the wet grinding mixing, the grinding medium is hexane, and the ball-to-material ratio is 2.5-2.0:1.

[0026] Preferably, the holding time of the holding section is greater than or equal to 30 minutes.

[0027] Preferably, the temperature rising rate of the second to fifth stages is 0.2-2.5 DEG C / min.

[0028] Preferably, the liquid phase sintering is a holding treatment at 1400-1460 DEG C for 1 hour.

[0029] Preferably, the vacuum heat treatment is a holding treatment at 600-650 DEG C for 28-32 hours.

[0030] According to the above technical solution, compared with the prior art, the present application has the following beneficial effects:

[0031] 1. The method of combining vacuum degree and heating rate is used to solve the densification problem of WC-Co-Ni-Cr-Al large product, and the metallographic porosity of the prepared large product is not less than A02B00.

[0032] 2. The change trend of vacuum degree value is used to observe and control in different stages of solid phase sintering, so as to accurately judge whether the AlN cracking is completed in the sintering process.

[0033] 3. The existing sintering equipment in the hard alloy industry is used, the change trend of vacuum value in the furnace and the design of heating rate are used to control the AlN cracking, the densification sintering of WC-Co-Ni-Cr-Al material is completed, no additional new equipment is invested, and batch production is facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiment or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0035] Figure 1 It is a general hard alloy sintering process schematic diagram.

[0036] Figure 2 It is a sintering process schematic diagram of the WC-Co-Ni-Cr-AlN material of the present application.

[0037] Figure 3 It is a low-power metallographic graph of Example 1 WC-32% (Co+Ni)-1.0% Cr-2.7% AlN.

[0038] Figure 4 It is a low-power metallographic graph of Comparative Example 1 WC-32% (Co+Ni)-1.0% Cr-2.7% AlN.

[0039] Figure 5 It is a low-power metallographic graph of Example 2 WC-24% (Co+Ni)-0.8% Cr-1.8% AlN.

[0040] Figure 6 It is a low-power metallographic graph of Comparative Example 2 WC-24% (Co+Ni)-0.8% Cr-1.8% AlN.

[0041] Figure 7 It is a low-power metallographic graph of Example 3 WC-15% (Co+Ni)-0.5% Cr-0.8% AlN.

[0042] Figure 8Example 3 WC-15% (Co+Ni)-0.5% Cr-0.8% AlN macrostructure. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort fall within the protection scope of the present application.

[0044] In the present application, the powder metallurgy method is adopted, and the sintering of the 40-45 kg single weight and 200 mm diameter block product made of the Co-Ni content 15-32% cemented carbide material is taken as an example for description. In general sintering process, the AlN cracking is not sufficient for the sintering of the WC-Co-Ni-Cr-AlN powder material, which can cause the Al oxide precipitation in the microstructure of the alloy and cause the alloy defects. The process in the solid phase sintering stage is designed for the alloy materials with different compositions.

[0045] Figure 1 It is a general cemented carbide sintering process schematic diagram. The solid phase sintering temperature is raised from 700 DEG C to 1320 DEG C, and the sintering furnace is in a negative pressure state. The temperature rising rate is 2.5 DEG C-5.0 DEG C / min. The temperature rising rate of the comparative example is 3.5 DEG C / min.

[0046] Figure 2 It is a sintering process schematic diagram of the WC-Co-Ni-Cr-AlN material in the present application.

[0047] The solid phase sintering temperature is raised from 700 DEG C to 1320 DEG C in stages, and the sintering furnace is in a negative pressure state. The vacuum degree and the temperature rising rate are monitored and controlled, and the different parameters are selected according to the alloy material composition, product weight and volume size, etc. according to Table 1.

[0048] Table 1 Solid phase sintering stage 700 DEG C-1320 DEG C temperature rising and vacuum degree control scheme

[0049]

[0050] The maximum vacuum degree in the P4 stage is taken as the basis for judgment, and the following situations are judged:

[0051] 1) When P4≤P1, P4

[0052] 2) When P4 is (1-2) times P1 or more, if P5 is adjusted to be less than or equal to P1, it can be determined that the AlN cracking in the sintering process of the WC-Co-Ni-Cr-Al material is completed; if P5 is not less than or equal to P1, the AlN cracking is not completed.

[0053] Example 1

[0054] The WC powder with a Fisher particle size of 20.0 μm 64.3 parts, Co powder 16 parts, Ni powder 16 parts, Cr powder 1 part, and AlN powder 2.7 parts were mixed. The amount of hexane added per kilogram of mixed powder was 0.30 L, the amount of paraffin added was 0.2 g, and the amount of cosolvent added was 0.02 g. The WC powder, Co powder, paraffin, cosolvent, and the like were mixed and loaded into a ball mill, the ball-to-material ratio was 2.5:1, the ball milling time was 28 h, and the green compact was obtained after unloading, drying, granulation, and pressing, with a green compact weight of 40.5 kg. Then, the scheme in Table 2 was used for solid phase sintering, and after the solid phase sintering was completed, sintering at 1400°C was performed for 1 h, and an alloy with a grain size of 2.43 μm and a porosity of A02B00 was obtained. After sintering, vacuum heat treatment was performed at a temperature of 620°C for 32 h. The metallographic structure is shown in Figure 3 Table 2, and the porosity was A04B06. The basic properties of the alloys of Example 1 and Comparative Example 1 are shown in Table 3.

[0055] Table 2, and the porosity was A04B06. The basic properties of the alloys of Example 1 and Comparative Example 1 are shown in Table 3.

[0056]

[0057] Comparative Example 1

[0058] The composition and the same conditions were used for wet milling, drying, granulation, and pressing to form a green body, which was then sintered. The process scheme was different from that of the solid phase sintering stage, and the other processes were the same. The temperature was raised at a rate of 3.5°C / min from 700°C to 1320°C, and the vacuum degree in the sintering furnace was in a negative pressure state. The metallographic structure is shown in Figure 4 Table 3, and the porosity was A04B06. The basic properties of the alloys of Example 1 and Comparative Example 1 are shown in Table 3.

[0059] Table 3, and the porosity was A04B06. The basic properties of the alloys of Example 1 and Comparative Example 1 are shown in Table 3.

[0060]

[0061]

[0062] Example 2

[0063] WC powder 73.4 parts, Co powder 12 parts, Ni powder 12 parts, Cr powder 0.8 parts, and AlN powder 1.8 parts having a Fisher particle size of 20.0 μm were mixed. The amount of hexane added per kilogram of mixed powder was 0.30 L, the amount of paraffin wax added was 0.2 g, and the amount of cosolvent added was 0.02 g. The WC powder, Co powder, paraffin wax, cosolvent, and the like were mixed and charged into a ball mill, the ball-to-charge ratio was 2.5:1, and the ball milling time was 28 h. After being unloaded, dried, granulated, and pressed, a green compact was obtained, and the weight of the green compact was 43 kg. Then, the green compact was subjected to solid phase sintering according to the schedule shown in Table 4, and after the solid phase sintering was completed, the sintering was performed at 1410°C for 1 h under a holding condition, thereby obtaining an alloy having a grain size of 2.39 μm and a porosity of A02B00. After the sintering was completed, vacuum heat treatment was performed at a temperature of 650°C for 28 h. The metallographic structure is shown in Figure 5 Table 4, and the vacuum degree and the temperature rising rate during the solid phase sintering stage were controlled as shown in Table 4.

[0064] Table 4 Control of vacuum degree and temperature rising rate

[0065]

[0066] Comparative Example 2

[0067] The component composition was the same as that of Example 2, and wet milling, drying, granulation, and pressing were performed under the same conditions. After the green compact was obtained, the green compact was subjected to sintering, and the sintering process was the same as that of Example 2, except that the schedule during the solid phase sintering stage was different. During the solid phase sintering stage, the temperature was raised at a rate of 3.5°C / min from 700°C to 1320°C, and the vacuum degree in the sintering furnace was in a state of negative pressure. The metallographic structure is shown in Figure 6 Fig. 2, and the metallographic porosity was A02B04. The partial properties of the alloy of Example 2 and Comparative Example 2 are shown in Table 5.

[0068] Table 5 Basic properties of the alloy of Example 2 and Comparative Example 2

[0069]

[0070] Example 3

[0071] WC powder 83.7 parts with Fisher particle size of 20.0 μm, Co powder 7.5 parts, Ni powder 7.5 parts, Cr powder 0.5 parts, and AlN powder 0.8 parts were mixed. The amount of hexane added per kilogram of mixed powder was 0.30 L, the amount of paraffin added was 0.2 g, and the amount of cosolvent added was 0.02 g. The WC powder, Co powder, paraffin, cosolvent, and the like were mixed and loaded into a ball mill, the ball-to-material ratio was 2.0:1, the ball milling time was 28 h, and after unloading, drying, granulation, and pressing, a green compact was obtained, the weight of the green compact was 42.0 kg. Then, the scheme in Table 6 was used for solid phase sintering, and after the solid phase sintering was completed, sintering at 1460 °C was performed for 1 h, an alloy with a grain size of 2.14 μm was obtained, and the porosity was A02B00. After sintering, vacuum heat treatment was performed at a temperature of 630 °C for 30 h. The metallographic structure is shown in Figure 7 Table 6, and no pores caused by Al oxide were found. The control of the vacuum degree and the heating rate during the solid phase sintering stage is shown in Table 6.

[0072] Table 6 Control of vacuum degree and heating rate

[0073]

[0074]

[0075] Comparative Example 3

[0076] The component composition was the same as that of Example 3, and wet milling, drying, granulation, and pressing were performed under the same conditions to obtain a green compact, which was then sintered. Except that the process scheme during the solid phase sintering stage was different, the other processes during the sintering stage were the same. During the solid phase sintering stage, the heating rate was 3.5 °C / min from 700 °C to 1320 °C, and the vacuum degree in the sintering furnace was in a negative pressure state. The metallographic structure is shown in Figure 8 Figure 2, and the porosity was A04B04. The partial properties of the alloy of Example 3 and Comparative Example 3 are shown in Table 7.

[0077] Table 7 Basic properties of the alloy of Example 3 and Comparative Example 3

[0078]

[0079] Through the comparison of the metallographic structure and mechanical properties of the examples and the comparative examples, it was found that after the implementation of the technical scheme, the densification of the sintered body of the WC-Co-Ni-Cr-Al material was improved, and through subsequent vacuum heat treatment, the strength and hardness of the alloy were greatly improved. In particular, the improvement of the strength of the alloy was most obvious. The solution of the densification problem of the WC-Co-Ni-Cr-Al material during the sintering stage played a positive role in the performance improvement of the alloy after subsequent heat treatment.

[0080] The various embodiments described in this specification are implemented in a progressive manner, each embodiment focusing on the differences from other embodiments, and the same or similar parts between embodiments can be mutually referred to. For the apparatus disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0081] The above description of disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for producing a cemented carbide containing the components WC, Co, Ni, Cr, Al, characterized in that The application relates to a preparation method of a hard alloy containing WC, Co, Ni, Cr and Al components. The AlN powder is mixed with coarse WC powder, Co powder, Ni powder and Cr powder through wet grinding, ball milling, drying, sieving, granulating, pressing into a green compact, and then removing a molding agent, solid-phase sintering, liquid-phase sintering and vacuum heat treatment in sequence; The solid-phase sintering comprises: a first stage of setting a heat preservation section at 700-800 DEG C, drawing a limit vacuum of less than 5Pa during the heat preservation, a second stage of heating at (700-800) DEG C-1000 DEG C, a third stage of heating at 1000 DEG C-1250 DEG C, a fourth stage of heating at 1250 DEG C-1290 DEG C and a fifth stage of heating at 1290 DEG C-1320 DEG C; The vacuum degrees in the five solid-phase sintering stages are monitored and are named as P1, P2, P3, P4 and P5 respectively, wherein P1 takes the minimum value and P2-P5 take the maximum value; When P4<=P1, P4 If P4>P1, the heating rate of the fifth stage is adjusted until P5<=P1, then it is judged that the AlN cracking in the sintering process of the WC-Co-Ni-Cr-Al material is completed; if the adjustment cannot reach P5<=P1, it is judged that the AlN cracking is not completed completely, and the alloy material is scrapped; The hard alloy containing WC, Co, Ni, Cr and Al components comprises the following components in percentage by mass: Co 7.5-16%, Ni 7.5-16%, Cr 0.5-1.0%, AlN 0.8-2.7% and the balance of WC; The mass ratio of Co to Ni is 1:

1. The particle size of the AlN powder is less than or equal to 2 microns. The fsss particle size of the coarse WC powder is greater than or equal to 20 microns.

2. A method of producing a cemented carbide containing components of WC, Co, Ni, Cr, Al, according to claim 1, characterized in that, In the wet grinding, the grinding medium is hexane, and the ball-to-material ratio is (2.5-2.0):

1.

3. A method of producing a cemented carbide containing components of WC, Co, Ni, Cr, Al, according to claim 1, characterized in that, The heat preservation time of the heat preservation section is greater than or equal to 30 minutes.

4. A method of producing a cemented carbide containing components of WC, Co, Ni, Cr, Al according to claim 1, characterized in that, The heating rate of the second to fifth stages is 0.2 DEG C / min-2.5 DEG C / min.

5. A method of producing a cemented carbide containing components of WC, Co, Ni, Cr, Al according to claim 1, characterized in that, The liquid-phase sintering is heat preservation treatment at 1400 DEG C-1460 DEG C for 1 hour.

6. The preparation method of the hard alloy containing WC, Co, Ni, Cr and Al components according to claim 1, wherein the vacuum heat treatment is heat preservation treatment at 600 DEG C-650 DEG C for 28-32 hours.

Images