JPH03140450A - Wear resistant alloy powder and member - Google Patents

Abstract

PURPOSE:To enlarge the tolerance for Fe and C contents and to improve wear resistance and corrosion resistance by increasing Cr content, combinedly adding specific amounts of B, Si, Ni, and Nb, and mixing a boride phase into an amorphous phase. CONSTITUTION:A wear resistant alloy powder has a composition consisting of, by weight, <=0.06% C, <=1.2% Mn, 3-4% Si, 3-4% B, 20-35% Cr, 2-3% Mo, 2-3% Nb, <=2% Fe, <=0.006% oxygen, <=0.006% nitrogen, and the balance essentially Ni, and further, a boride phase is mixed into an amorphous phase, by which a highly corrosion- and wear-resistant alloy powder can be obtained even if Cr content is increased. By plasma-spraying this wear resistant alloy powder on a base material under reduced pressure, a wear resistant member can be obtained. This member can be suitably applied to non-magnetic corrosion- and wear-resistant members applied to equipment operating in a magnetic field in high-temp. and high-pressure water and parts for plastic molding machine, concrete pump, etc.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a wear-resistant alloy powder and a wear-resistant member to which the same powder is applied, and in particular to a non-magnetic alloy powder applied to equipment that moves within a magnetic field in high-temperature, high-pressure water. The present invention relates to the same powder and members that can be suitably applied to corrosion-resistant and wear-resistant members, plastic molding machines, concrete pumps, cylinders such as high-temperature water gate valves, and various wear-resistant parts.

[Conventional technology]

As a conventional technology in the above field of application, for example, Japanese Patent Application Laid-open No. 48-
57818, JP-A No. 56-169740, and JP-B No. 56-53626, in order to improve wear resistance, carbon dioxide containing 5 to 45% by weight or containing Ni as the main component is disclosed. There are wear-resistant and corrosion-resistant alloys. Also,
In order to improve the corrosion resistance of these,
No. 42 proposes an alloy with an increased Cr content of up to 20% by weight.

[Problem to be solved by the invention]

Since the above-mentioned conventional alloys contain Co, from the viewpoint of reducing radiation exposure in nuclear power plants, there is a strong desire to use improved alloys that reduce the amount of Co as much as possible or new alloys that eliminate Co as an alternative material.

However, in the method of reducing the amount of Co and increasing the Ni content instead, there is a problem that the conventional high hardness and high wear resistance cannot be maintained unless the amount of Cr in the stable is reduced. is a barrier to the development of wear-resistant parts.

The present inventor previously applied for Japanese Patent Application No. 62-247694.
In No. 2-240675, it was shown that combined addition of Mo and Nb was effective as a method of obtaining high hardness without reducing the amount of Cr. That is, it was revealed that high hardness of HRC61.5 can be ensured with the Cr content increased to 14% by weight.

In view of the above-mentioned state of the art, the present invention aims to expand the permissible range of Fe and C content from the invention of Japanese Patent Application No. 62-247694 proposed earlier, and is a wear-resistant alloy with excellent wear resistance and corrosion resistance. The present invention aims to provide a powder and a wear-resistant member using the powder.

[Means to solve the problem]

In order to further improve the performance of the alloy disclosed in Japanese Patent Application No. 62-247694, the present inventor increased the Cr content in order to obtain a highly corrosion-resistant and wear-resistant alloy that can withstand severe corrosive environments, and the resulting hardness As a result of intensive research into methods to compensate for the decrease in hardness, we have adopted the method proposed in the previous invention to prevent the decrease in hardness due to the combined addition of Mo and Nb.
Furthermore, B, which is a metalloid, Si, and Ni, which is a transition metal fellow,
We found that a highly corrosion-resistant and wear-resistant alloy can be obtained even if the Cr content is increased by causing partial amorphization in combination with Nb and by mixing the amorphous phase by using a rapid cooling method using gas atomization. Obtained.

The present invention was completed based on the above findings, and includes: (1) In weight%, C: 0.06% or less, Mn: 1.2%
Below, Si: 3-4%, B: 3-4%, Cr: 20-3
5%, Mo: 2-3%, Nb: 2-3%, Fe: 2%
Hereinafter, a wear-resistant alloy powder having a composition consisting of oxygen: 0.006% or less, nitrogen: 0.006% or less, and the remainder substantially Ni, and in which a boride phase is mixed in an amorphous phase.

(2) A wear-resistant member formed by spraying the above-mentioned wear-resistant alloy powder onto a base material by low-pressure plasma spraying.

[Effect]

The reasons for limiting the alloy composition and thermal spraying method of the present invention will be explained below. Hereinafter, % means weight %.

Cr is an essential component for improving hardness and corrosion resistance by boride. Particularly when emphasis is placed on improving corrosion resistance and stress corrosion cracking resistance, the content should be 20% or more. However, if it exceeds 35%, the hardness of the sprayed layer will begin to decrease.
The Cr content is limited to 20-35% by weight.

B becomes boride and increases the hardness of the precipitated alloy, but if it is less than 3%, the hardness as a high hardness Ni-based alloy is insufficient, and if it exceeds 4%, free B appears. Since it makes the alloy brittle, it is set at 3 to 4%.

Si is also an effective component for increasing the hardness of Ni-based alloys, and like B, it can be added in large amounts, plays a large role in increasing the hardness, and is also effective as a deoxidizing agent. If it is less than 3%, the effect will be insufficient, and if it exceeds 4%, the alloy will become brittle, so the content is set at 3 to 4%.

B and Si each have the above-mentioned effects when used alone, but by appropriately containing them in combination, it is possible to obtain hardness suitable for workability and wear resistance while maintaining toughness. Preferably, the total amount is about 6.5 to 7.5.

Mo is an important component that significantly contributes to increasing the hardness of the alloy of the present invention, but if it is less than 2%, its effect is insufficient, and if it exceeds 3%, the hardness decreases. Therefore, M
The content of O is 2 to 3%.

Nb has an added effect in the presence of Mo.

That is, it is a component that contributes to an increase in hardness by coexisting with Mo. It is also one of the components necessary for amorphization. If the amount added is less than 2%, the effect is insufficient;
%, on the contrary, the hardness decreases. Therefore, Nb is set at 2 to 3%.

Fe is an impurity, but in an alloy containing 20% or more of Cr, if it is contained in an amount exceeding 2%, it will impair demagnetization, so it should be kept at 2% or less.

Mn is also an impurity, but if it exceeds 1.2%, it will impair nonmagnetism and corrosion resistance, so it should be kept at 1.2% or less.

Co forms a compound with itself or with Ni, Cr, Si, and B to improve wear resistance and galling resistance, but it leads to an increase in radiation exposure due to induced activation. Also, since the material cost increases, the amount of impurities is unavoidable.

C precipitates a large amount of carbides (Cr-depleted parts) which are unfavorable for corrosion resistance, and has a particularly strong bond with Nb, resulting in the formation of NbC, which impairs the synergistic effect with Mo, so it is better to keep it as low as possible, 0.06% or less. shall be.

Oxygen and nitrogen are impurities, but since they are used as a thermal spray material, it is better to reduce them as much as possible. Therefore, each 0.0
It should be less than 0.6%.

The wear-resistant alloy powder of the present invention is obtained by the gas atomization method, and the powder particles of this type of alloy that are rapidly solidified and cooled by this method have a non-equilibrium amorphous structure, which is much harder than the molten material. High hardness can be obtained.

In addition, the wear-resistant alloy powder of the present invention is applied by low-pressure plasma spraying, but in order to reproduce rapid solidification and cooling effects, the spraying speed is low (the concentration of the sprayed particles is dilute). Because of this, the cooling heat capacity of the surrounding area (atmosphere including the base material) for the sprayed particles is relatively large. It is advantageous compared to etc. In addition, it is easy to control the preheating temperature of the base material, and it is possible to obtain a dense thermal sprayed material with few oxides and pores, so it has excellent cracking resistance, high toughness, and peeling resistance. Due to its advantages, low pressure plasma spraying is essential as a thermal spraying method.

〔Example〕

Eight types of alloy compositions were melted in a 20 kg capacity vacuum high frequency induction furnace to obtain ingots (melted materials) having the compositions shown in Table 1. Initial permeability μ for each ingot. Measurements and hardness tests were conducted. The results are also listed in Table 1. Next, each ingot was heated to 1500℃ in a gas atomization rig.
The powder was remelted and quenched with nitrogen gas at a spray pressure of 25 kgf/Cd, a spray time of about 3 minutes, and a spray gas volume of 70 m''. Using the obtained alloy powder (average diameter: 42 μm), a second
Low-pressure plasma spraying was performed under the temperature history shown in the figure and an argon gas atmosphere of 10-' Torr.

Figure 2 shows the temperature change over time from the start of preheating the alloy before thermal spraying to the end of thermal spraying, with a hot junction of a thermocouple attached to the surface (boundary surface) of the base material. This occurs because the thermal spray gun repeatedly moves back and forth.

It is desirable for the alloy (base material) to be a material that has high hardness commensurate with high-hardness thermal sprayed materials and has a certain degree of heat resistance (does not soften, has oxidation resistance, etc.), and in this case Inconel 71 is used.
An 8-material thermal alloy was used. In addition, it is difficult to cut and process into wear test pieces after thermal spraying, so Inconel 718 material is processed in advance into a predetermined test piece shape and size (wear test piece), and then thermal sprayed on one side that will be the test surface. After spraying, the outer surface of the sprayed layer was simply polished with a diamond grindstone so that it could be used for wear tests.

After thermal spraying, the appearance, cross-sectional microstructure, and hardness of the test piece were tested. As a result, no cracks or peeling due to thermal stress were observed in the thermally sprayed material, and the structure was dense. As shown in Table 1 and Figure 1, the hardness is HV (0,2) 1000 for all alloys except for alloys in which Nb and Mo are not added in combination.
It was found that ultra-high hardness of HV (0.2N 200) can be stably obtained by limiting the Cr content to 30% or less.

Furthermore, wear tests were conducted on the thermal sprayed material of Alloy 4 (outside the invention) 7 (invention) and the melted material of Alloy 7 (invention) under the test conditions shown in Table 3. As a result, the results are shown in Table 2. The thermal sprayed material of Alloy 7 has a specific wear amount that is one order of magnitude smaller than that of the thermal sprayed material of Alloy 4 and the melted material of Alloy 7, and a very small change in roughness [Roughness after wear test (R, , , ) - Wear test It is clear that the Alloy 7 thermal sprayed material has excellent wear resistance properties, as it shows the previous roughness (R,,,,)] and also reduces the amount of wear on the fixed piece of the mating material (Stellite Nα25). became.

Table 3 [Effects of the Invention] (1) According to the present invention, in order to improve wear resistance and corrosion resistance and reduce material costs by increasing the allowable amounts of impurities Fe and C, the amount of Cr is increased. The amount can be increased to more than twice the optimum amount, that is, 20 to 35%, and Re and C can be increased to 2% and 0.0%, respectively, for the melting material.
Even when increased to 0.06%, a wear-resistant and corrosion-resistant alloy powder is obtained that exhibits a low initial permeability of 1.0023 and maintains the desired non-magnetism. As a result of thermal spraying on the base material, HV (0
, 2) It was revealed that a surface hardened layer having an extremely high hardness of 1200 and good adhesiveness could be obtained.

(2) In addition, improvements in galling resistance and abrasion resistance of the wear-resistant member were observed in a wear test. On the other hand, although no particular tests were conducted regarding corrosion resistance, it is clear that it is improved. This thermal sprayed material has a combination of Mo and Nb addition and low-pressure plasma spraying, and even with an increased amount of Cr, a metal structure with excellent hardness and toughness with excellent wear resistance can be obtained, resulting in cracking, peeling, and chipping. Provided is a wear-resistant member that does not cause such problems.

(3) The reason for the remarkable improvement in hardness due to thermal spraying is that the rapid cooling (estimated at 1000
°/S or more) and the resulting amorphous (
It is thought that a mixed phase of amorphous) and boride is generated. Although it is a highly hard material, no cracking or peeling is observed.In addition to the characteristics of amorphous, such as being more viscous and easier to work with than crystalline materials, it is also possible to use high-temperature thermal spraying at temperatures below approximately 420°C. It seems that the application is effective.

[Brief explanation of the drawing]

FIG. 1 is a hardness distribution chart of the thermal spray material according to the first embodiment of the present invention, and FIG. 2 is a base material surface temperature history chart during reduced pressure plasma spraying. Figure 1

Claims (2)

[Claims] (1) In weight%, C: 0.06% or less, Mn: 1.2%
Below, Si: 3-4%, B: 3-4%, Cr: 20-3
5%, Mo: 2 to 3%, Nb: 2 to 3%, Fe: 2% or less, oxygen: 0.006% or less, nitrogen: 0.006% or less, and the balance consists essentially of Ni. A wear-resistant alloy powder consisting of an amorphous phase mixed with a boride phase. (2) A wear-resistant member obtained by spraying the wear-resistant alloy powder according to claim (1) onto a base material by low-pressure plasma spraying.