JPS6219499B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides wear resistance and scuffing resistance,
This invention relates to a self-fusing alloy for surface hardening that has excellent pitting resistance. Self-fusing alloys for thermal spray welding or overlay have been well known as surface hardening materials for mechanical parts that require wear resistance. Among these, the self-fusing alloys used for surface hardening of the pad surface of the valve rocker arm of automobile engines are:
There are Ni-based, Co-based, or Fe-based self-fusing alloys, and these alloys are used depending on the conditions along with other surface hardening methods, chrome plating, chill structure cast iron, nitriding treatment, and carburizing and quenching treatments. As is well known, the pad surface of the valve rocker arm of an automobile engine, which is the part that contacts the lead surface of the camshaft, is required to have a high degree of wear resistance, scuffing resistance, and pitting resistance, but none of the above surface hardening methods can be used. There are advantages and disadvantages to both. For example, chrome plating is prone to scuffing, and chilled cast iron is prone to pitting and wear. Nitriding treatment and carburizing and quenching treatment have insufficient wear resistance. Therefore, self-fusing alloys
In recent years, thermal spray welding or overlaying has been carried out on the pad surface of valve blocker arms, but Ni
Base self-fusing alloys have the disadvantage that scuffing and pitting occur rapidly when metal-to-metal sliding occurs at high speeds and under high loads, or when lubrication conditions deteriorate.
Co-based self-fluxing alloys have a small amount of wear on themselves, but have the disadvantage of causing severe wear on the other materials that come into contact with them. Furthermore, Fe-based self-fluxing alloys, contrary to Ni-based and Co-based self-fluxing alloys, have good scuffing resistance and pitting resistance, and cause almost no wear on the mating material, but they have the disadvantage of a large amount of wear themselves. The alloy of the present invention corrects the shortcomings of conventional self-fusing alloys, improves its own wear resistance, and provides a self-fusing alloy that also improves scuffing resistance and pitting resistance and reduces wear of mating materials. The composition of the alloy is Fe6~22%, Cr8~15
%, Si3~9%, B1~3%, C0.3~1.5%, Mo1~
8% Cu, 1 to 5% Cu, and the remainder substantially Ni. The limited ranges of each constituent element of the alloy of the present invention will be described below. Si is an element that imparts self-solubility together with B, and is an important element for generating nickel silicide, increasing the hardness of the alloy itself, and improving wear resistance, scuffing resistance, and pitting resistance. . If the Si content is less than 3%, these characteristics cannot be sufficiently obtained, whereas if it exceeds 9%, the hardness becomes too large and becomes brittle, and cracks are likely to occur during processing or use. Therefore, Si was set at 3 to 9%. Like Si, B is an element that imparts self-solubility to the alloy, and is an effective element for combining with Cr to form boride, increasing hardness, and improving wear resistance. If B is less than 1%, the effect is not sufficient, and 3
% or more, boride is generated more than silicide,
Scratching resistance deteriorates. Therefore B is 1
~3%. C is an element that combines with Cr to form carbide, and also forms a solid solution in the matrix, increasing the hardness and wear resistance of the entire alloy. C is 0.3
If it is less than 1.5%, the formation of carbide will be insufficient, resulting in poor wear resistance, and if it exceeds 1.5%, the amount of carbide will be too large, resulting in high hardness but poor scuffing resistance. Therefore, C was set at 0.3 to 1.5%. Cr is an essential element that combines with B and C to form borides and carbides, increasing hardness and improving wear resistance. If the Cr content is less than 8%, the formation of chromium boride and chromium carbide will be insufficient, resulting in insufficient hardness and poor wear resistance. But 15
%, the formation of chromium boride and chromium carbide will be sufficient and the hardness will increase, but the melting point of the alloy will rise and the self-fluxability, which is the basic characteristic of the present invention, will be inhibited, making it difficult to harden the surface by thermal spray welding or overlay welding. becomes difficult. Therefore, Cr was set at 8 to 15%. Fe forms a matrix with Ni, improves the solid solubility of C in the matrix, and increases the hardness of the matrix itself, thereby helping to improve the hardness of the entire alloy. The higher the hardness of the matrix, the smaller the difference in hardness from the surrounding nickel silicide, chromium boride, and chromium carbide, making scuffing and pitting less likely to occur. If Fe is less than 6%, it is insufficient to increase the hardness of the matrix, and if it is more than 22%, surface hardening of this alloy becomes difficult and the grindability becomes significantly poor. Therefore, Fe was set at 6% to 22%. Mo forms a solid solution in the Ni and Fe matrix and has the effect of increasing the strength of the alloy itself. If Mo is not added, cracks will occur on the test surface when a wear test is performed under high speed and high load conditions as shown in the example.
When Mo is added, cracks no longer occur. The effect can be expected from 1% or more, but if it is 8% or more, the opposite effect occurs and cracks are more likely to occur than with no additives. Therefore, the amount of Mo added is 1~
It was set at 8%. Cu forms a solid solution in the Ni matrix, and has the effect of structurally stabilizing the chromium boride and chromium carbide that precipitate around it. If Cu is less than 1%, chromium boride and carbide are likely to segregate, causing pitting. But 5
If it exceeds %, the precipitation effect becomes large and it becomes brittle. Moreover, self-solubility is also inhibited, which is not preferable. Therefore, the amount of Cu added was set to 1 to 5%. Next, examples of the alloy of the present invention will be described. Example 1 Various self-fusing alloy powders shown in Table 1 were prepared, and a hardened surface film with a thickness of approximately 1.5 mm was formed on a mild steel base material by gas spray welding, and the surface was mirror-finished and used as a test piece. And so. The test piece was then pressed against a rotating piece rotating at high speed as shown in FIG. 1, and tested under the following conditions using an apparatus for performing an abrasion test by sliding metal pieces together in a state of boundary lubrication. Rotating piece material: Special alloy chilled cast iron Number of revolutions: 3370rpm Test load: 40Kg Lubricating oil: White spindle oil Lubricating oil temperature: 70°C Temperature control Test time: 5 hours After the test, the size of the wear marks on the test piece (mm ² )
The overall wear resistance was evaluated by measuring the scuffing state (striped kiss) and pitting state (partial chipping) of the scratch surface, and measuring the wear loss (mg) of the rotating piece. . The test results are summarized in Table 2. As is clear from Table 2, compared to the conventional self-fusing alloys (Samples No. 8 to 12), the self-fusing alloys of the present invention (Samples Nos. 1 to 7) have larger wear scars and wear amount of rotating pieces. The alloy showed well-balanced wear resistance, little scuffing and pitting, and good compatibility with the mating material, indicating that it is an alloy with excellent overall wear resistance.

【table】

[Table] Example 2 Surface hardening of self-fusing alloy sample No. 3 of the present invention and comparison materials such as chrome-plated products, chill structure cast iron products, and conventional self-fusing alloy sample No. 8 on actual valve rocker arm pad surfaces. We installed it on a test machine similar to an actual engine and conducted a wear test under the following test conditions. Engine speed: 1000rpm Lubricating oil: Engine oil (10W30) Test time: 200hr The results of the test are shown in Table 3. It has been found that the self-fusing alloy of the present invention has superior wear resistance to comparative materials that have been used as actual valve rocker arm pad materials.

[Table] Example 3 Self-fusing alloy sample No. of the present invention tested in Example 2.
3 and conventional self-fusing alloy sample No. 8 with a particle size of 100 mesh or less, formed into a sheet approximately 1 mm thick with a binder whose main component is acrylic resin, and pasted on the pad surface of the rocker arm. , then heated to 1000℃ in a batch vacuum furnace.
After being held at 10 ^-3 Torr for 10 minutes, it was taken out in a gas-cooled state. The Rocker arm surface-hardened using this method exhibited good appearance and cross-sectional structure without surface sag or peeling. When the thus surface-hardened material was subjected to the same wear test as in Example 2, the results were exactly the same as those shown in Table 3.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main body configuration of the wear tester used in Example 1 of the present invention. 1: Base material, 2: Surface hardening film, 3: Rotating piece,
4: Lubricating oil, P: Loading direction.

Claims (1)

[Claims] 1 Fe6~22%, Cr8~15%, Si3~9%, B1~3
%, C0.3 to 1.5%, Mo1 to 8%, and Cu1 to 5% as essential components, and the remainder substantially consists of Ni.