JPH042761A - Wear-resistant composite material and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application]
The present invention relates to a wear-resistant composite material that has a high thickness and high density by combining e-base materials, and a method for producing the same.

[Prior Art] Conventional methods for producing wear-resistant composite materials by coating a base material with wear-resistant materials include the following.

(1) Capsule HIP method As shown in FIG. 7, in this method, a base material 1 is surrounded by a capsule 2 that matches the shape of the base material 1, and the required wear-resistant powder alloy 3 is placed in the space between the capsule 2 and the base material 1. In this method, the powder alloy 3 is filled, degassed and sealed, and then subjected to hot isostatic pressure treatment (hereinafter referred to as HIP treatment) to sinter and coat the powder alloy 3.

However, although this method allows the film to be thickened to some extent, there is a problem in that the capsule processing cost is high for products with complex shapes such as curved surfaces.

(2) Thermal spraying method This method uses plasma spraying to coat wear-resistant alloys, and is particularly suitable for products with complex shapes, but the presence of pores in the coating layer is unavoidable and the coating layer is dense. be lacking. Another problem is that the bonding force with the base material interface is weak.

(3) Method of performing HIF treatment after thermal spraying If HIP treatment is performed after thermal spraying in the above (2), it is possible to improve the quality of the coating.

However, with the conventional thermal spraying method, it is not possible to thicken the coating due to the above problems, and the coating is generally 0.5 to 1.5 degrees thick.
It was difficult to make the film thicker than this.

(4) Method of Japanese Patent Publication No. 58-39228 This method involves thermally spraying powder of heat-resistant and wear-resistant alloys such as Fe-based base materials W, Mo, Co, N1-based alloys, and self-fluxing alloys containing WC and VC.
This is a coating method that includes subsequent HIP treatment, and is a method that belongs to (3) above.

However, even with this method, thickening of the film is not targeted, and high-speed steel is not included in the thermal spray material. Furthermore, gas spraying and plasma spraying are shown as thermal spraying methods, but this plasma spraying method is understood to be performed under normal pressure, and there is no description suggesting the application of low-pressure plasma spraying.

[Problems to be Solved by the Invention] A problem common to the above-mentioned conventional methods is that the film layer cannot be made large. Even if this were possible (for example, the capsule HIP method described in (1) above), it would be practically impossible due to problems such as lack of compactness and bonding strength.

The reason why it is impossible to thicken the film using thermal spraying is that the internal stress generated by the rapid cooling of the sprayed particles (this is due to volume change due to thermal contraction and phase transformation during cooling) increases with the film thickness. However, the pores and oxides inside the film weaken the resistance to cracking, and the lack of adhesion between the film and the base material weakens the resistance to peeling. It will be done.

On the other hand, if it becomes possible to increase the thickness of the film, it can be applied to products with particularly complex shapes, such as guide rolls used in production lines for steel bars and wire rods. Since it can be reused any number of times, it has great advantages in terms of durability and cost.

Therefore, in order to obtain a high film thickness, the present inventors first conducted various tests on high-speed steel, which has excellent wear resistance and hot hardness, in selecting a film material. It was confirmed that the manufacturing process was sufficient to achieve the purpose.

Therefore, an object of the present invention is to provide a composite material having a high film thickness, which is inexpensive and highly wear resistant, and a method for manufacturing the same, based on the above findings.

[Means for Solving the Problems] A wear-resistant composite material according to the present invention that achieves the above object has a thickness of 3. It consists of a combination with a thermal spray coating of mm or more.

The high-speed steel used as the thermal spraying material may be W-based, Mo-based, or V-based, which are known to have excellent wear resistance and hot hardness, but among them, high-V steel is suitable.

To manufacture this wear-resistant composite material, the base material is first
The base material is preheated to 0° C. or higher, and then a low-pressure plasma spraying method is applied to the surface of the base material under this preheating temperature to spray the above-mentioned high-speed steel-based thermal spray material to form a coating.

The plasma spraying in this case is performed under a reduced pressure atmosphere with an oxygen partial pressure of 2 Torr or less and a total pressure of 20 to 300 Torr.

Thereafter, HIP treatment is performed to densify the film layer.

Furthermore, instead of the above-mentioned HIP treatment, the coating layer may be quenched and tempered. Furthermore, both this HIP treatment and heat treatment may be performed.

[Function] First, by combining the composite materials with a Fe-based base material and a coating material of high-speed steel, the features of high-speed steel, such as wear resistance and hot hardness, can be fully demonstrated. can. In addition, since the coefficients of thermal expansion of both materials are close to each other (for example, the coefficient of linear expansion of carbon steel is 11×10-6/"C, and the coefficient of linear expansion of high-speed steel is 11×10-6/"C), preheating is required after thermal spraying. It can suppress thermal stress during cooling from temperature to room temperature, and has high adhesion between the film and the base material.

Next, by preheating the base material to 600°C or higher before thermal spraying, it is possible to prevent the thermal spray particles from rapidly cooling, which reduces internal stress due to thermal distortion between the thermal spray particles, and also to reduce the internal stress caused by thermal distortion between the thermal spray particles. Since activation is maintained, internal stress is relaxed. As a result, even if the film is thick, peeling or cracking of the film is less likely to occur.

Figure 3 shows that the oxygen partial pressure and total atmospheric pressure are within the specified values above.
This is a diagram that examines the minimum substrate preheating temperature that should be used to obtain a film thickness of mm or more, and it is possible to form a film without peeling by changing the substrate preheating temperature ("C). It represents the maximum film thickness (w).From Figure 3, film thickness 3
It can be seen that in order to obtain a temperature of 600° C. or higher, the base material preheating temperature should be maintained at 600° C. or higher.

Next, under the above preheating temperature conditions, JIS
High speed steel powder equivalent to G 4403 was heated to an oxygen partial pressure of 2 Torr.
A film is formed by plasma spraying under a reduced pressure atmosphere with a total pressure of 20 to 300 Torr.

First, by limiting the oxygen partial pressure to a low level, oxidation of the substrate and thermal spray particles during preheating is prevented. Therefore, oxides that cause cracks in the film are reduced.

Figure 1 shows the effect of oxygen partial pressure (Torr) on transverse rupture force ()cg
This is a diagram examined based on the change in 2). From this diagram, it can be seen that the lower the oxygen partial pressure, the more stable the transverse rupture force is, and the lower the oxygen partial pressure is
When Torr is exceeded, the transverse rupture strength and, in turn, the resistance to cracking of the coating are likely to decrease rapidly.

Next, by setting the total atmospheric pressure to the above-mentioned low pressure condition, the heating and melting of the sprayed particles is promoted and the particle flight speed is increased, so the pores in the film are reduced and the density is improved, resulting in wear resistance. Improves sex. Furthermore, since the gas pressure in the pores is low, it is convenient for the HIP treatment in the post-process.

Figure 2 shows the total atmospheric pressure (
This is a diagram in which the influence of pore volume (%) in the film was examined by changing the pore volume ratio (%) of the film.If the total atmospheric pressure is 300 Torr or less, almost no pores are formed. Note that the lower limit value of the total pressure is determined from the viewpoint of practical economy.

Finally, HIP treatment is performed to eliminate the few remaining pores in the film and completely densify it. In addition, HI
P conditions are 1100℃ x 1500kg/cd
It is set as 1 hour.

Even if quenching and tempering is performed instead of this HIP treatment, the same level of density can be obtained. Furthermore, it goes without saying that quenching and tempering may be performed after the HIP treatment.

A microscopic photograph of the film structure after heat treatment is shown in FIG. 4(a). For comparison, FIG. 4(b) shows a microscopic photograph of the film structure as it was treated by the conventional capsule HIP method. Note that the base material and coating material are the same for both.

Comparing the two, it is clear that the film structure of the present invention has been significantly densified, and the carbides such as w and v are 5μ
It can be seen that the particles are finely divided to less than m and are uniformly dispersed.

[Example] In the present invention, the following tests were conducted in order to investigate the effects of substrate preheating temperature, oxygen partial pressure, and total atmosphere pressure.

The test was conducted in three stages.

Test 1: First, a dense film without pores was formed, and then, from the viewpoint of oxide inclusion, the upper limit of the oxygen partial pressure in the spraying atmosphere without reducing the transverse rupture strength was investigated.

Test 2: Next, since the presence of pores reduces wear resistance, the upper limit of the total pressure of the thermal spraying atmosphere that completely eliminates pores was investigated by <I (IP treatment) following thermal spraying.

Test 3: Finally, the preheating temperature of the base material at which a film thickness of 3 dragons or more could be formed while satisfying the above-mentioned double-stripe property was investigated.

Test conditions and results Common conditions Coating material 5KHIO equivalent composition alloy powder Particle size 100μm or less Low pressure plasma spraying machine Ar-20%H2 Thermal spraying machine Plasma gas spraying Current Base material Base material dimensions 00 A 45C Diameter 80 mra, height 100 m + * Cylindrical body (see Figure 5, 1 is the base material and 4 is the coating) Test 1 Base material preheating temperature 800°C Total atmosphere pressure 100 Torr Coating thickness 5 mm HIP conditions after thermal spraying 1100°C x 1500 kg /
cd X I Hr heat treatment quenching 1230
℃X 1.5win Heating then oil cooling tempering 550℃X8Hr Heating then air cooling Test method and results From film 4, a round rod-shaped test piece with a diameter of 5 mm was taken.
Transverse rupture strength was determined using a point bending tester.

The results are shown in FIG.

From this, from the point of view of film quality, the oxygen partial pressure should be set at 2 Torr.
It became clear that the following had to be done.

Test 2 Base material preheating temperature 800℃ Oxygen partial pressure 2 Torr Coating thickness 3mm HIP conditions after thermal spraying 1100℃X 1500kg /
cd

The results are shown in FIG.

From this, it has become clear that in order to obtain a dense film completely free of pores after HIP, the total pressure of the atmosphere during thermal spraying must be 300 Torr or less.

Test 3 Atmospheric total pressure: 100 Torr Oxygen partial pressure: 2 Torr Test method and results When the test specimen was cooled to room temperature after thermal spraying, the maximum film thickness without peeling of the film was determined.

The results are shown in FIG.

From this, it became clear that under the conditions for forming a film with good quality as determined in Tests 1 and 2, it is necessary to preheat the substrate at a temperature of 600° C. or higher in order to obtain a thick film of 3 mm or more.

EXAMPLES Tests were conducted using the basic conditions described below and varying the conditions related to the present invention.

The test conditions and test results are shown in Table 1.

First, we determined the film thickness that would not cause peeling or cracking of the film. The object of the present invention is to provide conditions under which a film having a temperature of 311° C.m or higher can be obtained.

Next, test materials were prepared with a film thickness within a range that provided a film without cracking or peeling, and after HIF treatment, various test pieces were taken to examine performance.

The density of the film was determined by examining the volume ratio of pores under a microscope for the sample after HIP treatment, and a completely dense state with no pores was defined as 100% density.

In the transverse rupture strength test and the wear test, the high-speed steel coating material was subjected to quenching and tempering before being subjected to the test.

Abrasion resistance was evaluated using an Amsler abrasion tester. This test method uses 345C diameter 40mm as shown in Figure 6.
A test piece 6 was pressed against the outer peripheral surface of a rotating disk 5 with a thickness of 3 mm with a force of 50 kg while water was being applied, and a friction distance of 5
The test was carried out by measuring the wear width of the test piece 6 after sliding it for 00 m.

Test conditions Base material Base material Dimensions Covering material 45C Cylindrical body with diameter 80 mm and height 10011I+1 (see Figure 5) A: 5KH10 equivalent composition Powder particle size 100 μm or less B: Carbide powder (VC-17%Co) Particle size 100 μm or less Thermal spraying conditions Plasma spraying test piece No. 1 to 7-Low pressure plasma spraying test piece No.
, 8 - Normal pressure plasma spraying plasma gas Ar-2
0%H2 Current 800 A HIP conditions after thermal spraying 1100℃X 1500kg /
cd
It can be seen that samples 3) to 3) are excellent in all aspects of film thickness, transverse rupture strength, density, and abrasion resistance.

Furthermore, even if a high film thickness can be obtained, test Nα4.5.6 shows that the substrate preheating temperature, oxygen partial pressure, and total atmosphere pressure are important for the quality of the film.

In Tests NG, 7, and 8 shown as comparative materials, cracking and peeling of the film occurred, making them unusable. In particular, the normal pressure plasma spraying method (Test No. 8) cannot provide a coating.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an inexpensive composite material with excellent wear resistance and durability.

Furthermore, it is possible to make the film thicker and more dense.

[Brief explanation of drawings]

Figure 1 is a diagram examining the influence of oxygen partial pressure from the perspective of transverse rupture strength when applying the low-pressure plasma spraying method in the present invention;
The figure is a diagram similarly examining the influence of the total atmospheric pressure from the perspective of pore volume fraction, Figure 3 is a diagram similarly examining the influence of substrate preheating temperature from the aspect of maximum film thickness, and Figure 4 (a). (b) is a photograph of the film structure comparing the present invention and the conventional case, FIG. The figure is an explanatory diagram of the conventional capsule HIP method. 1... Base material 4... Film agent Patent attorney Muneharu Sasaki

Claims (4)

[Claims] (1) A wear-resistant composite material comprising an Fe-based base material and a thermal sprayed coating with a thickness of 3 mm or more, the main component of which is high-speed steel, applied to the surface of the base material. (2) A Fe-based base material is heated to 600°C or higher in advance, and a material mainly composed of high-speed steel is applied to the surface of the base material under a reduced pressure atmosphere with an oxygen partial pressure of 2 Torr or less and a total pressure of 20 to 300 Torr. A method for manufacturing a wear-resistant composite material, which comprises forming a film by plasma spraying and then subjecting it to hot isostatic pressure treatment. (3) The method for manufacturing a wear-resistant composite material according to claim 2, wherein a heat treatment of quenching and tempering is performed after the plasma spraying. (4) The method for manufacturing a wear-resistant composite material according to claim 2, characterized in that a heat treatment of quenching and tempering is performed after the hot isostatic pressure treatment.