JP2686342B2 - High strength heat resistant alloy for injection molding powder metallurgy for high temperature structural members - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-strength heat-resistant alloy for injection molding powder metallurgy, which is applied to a high-temperature structural member of a gas turbine, and particularly about 500 ° C. such as in a boiler and an internal combustion engine. The present invention relates to the same alloy that is advantageously used for high temperature structural members used in the above environment.

[Conventional technology]

Conventionally, injection molding powder metallurgy materials have not been applied to high temperature structural members such as gas turbines that are used under high temperature and stress of 500 ° C or higher.

[Problems to be solved by the invention]

The particle size of alloy powder for injection molding powder metallurgy is generally the average particle size.
About 10 to 20 μm is required, and its production is generally a water atomizing method. However, the precipitation-strengthened heat-resistant materials conventionally used for gas turbine high temperature structural members (forged and cast materials) cannot produce powders applicable to injection molding powder metallurgy by the water atomizing method. Further, the precipitation-strengthened heat-resistant material can be pulverized by the gas atomizing method of producing powder in an inert atmosphere, but it is necessary to produce powder having an average particle size of about 10 to 20 μm required for injection molding powder metallurgy. It is difficult.

In view of the above-mentioned state of the art, the present invention is to provide a high-strength heat-resistant alloy having a chemical composition which can be produced by a water atomizing method for applying an injection-molded powder metallurgy material to a high-temperature structural member.

[Means for solving the problem]

The present invention is a high-strength heat-resistant alloy for injection molding powder metallurgy, which can be used at a high temperature of 500 ° C. or higher, and in% by weight, C: 0.
2 to 0.6, Cr: 15 to 25, Ni: 15 to 25, Co: 15 to 30, Mo: 5-1
5, W: 1 to 8 and Nb: 1 to 8 are contained, and the rest is Fe and inevitable impurities.

[Action]

 The reasons for limiting the components of the present invention are described below.

(A) C forms a solid solution in the austenite matrix to form Cr, W, Mo, Nb and carbides that enhance the high-temperature strength of the matrix, strengthen the grain boundaries and the inside of the grain, lower the melting point of the alloy and reduce the sinterability. Although there is an improving effect, if the content is less than 0.2% the desired effect described above cannot be obtained, while if it exceeds 0.6%, the strength decreases, so its content is 0.
It was set at 2 to 0.6%.

(B) Cr is an essential austenite constituent element for imparting excellent high temperature oxidation resistance. If the content of Cr is less than 15%, the desired excellent high temperature oxidation resistance cannot be secured. If added in excess, the high temperature strength deteriorates, so its content was set to 15-25%.

(C) Ni has the effect of improving the high temperature strength in the coexistence with Cr, but if its content is less than 15%, the desired effect described above cannot be obtained, while if it exceeds 25%, it is resistant to high temperature corrosion. Since its properties deteriorate, its content is defined as 15-25%.

(D) Co has the effect of increasing the creep strength, and if the content of Co is less than 15%, the above-mentioned desired effects cannot be obtained.
%, The high temperature oxidation resistance will deteriorate.
Its content was defined as 15% to 30%.

(E) Mo is the most important alloying element that imparts high temperature creep strength in the alloy of the present invention, and requires at least 5%, but if it is added in excess of 15%, the toughness deteriorates. Was defined as 6 to 15%.

(F) W has a function of imparting high temperature creep strength,
If the content is less than 1%, the above-described desired effect cannot be obtained. On the other hand, if the content exceeds 8%, the high temperature oxidation resistance tends to deteriorate, so the content was defined as 1 to 8%.

(G) Nb has a function of imparting high temperature creep strength,
If the content is less than 1%, the above-mentioned desired effect cannot be obtained, while if it exceeds 8%, the toughness deteriorates, so the content was defined as 1 to 8%.

〔Example〕

The alloy of the present invention and the comparative alloy were melted in an atmospheric high frequency induction melting furnace and cast into an ingot of nominally 10 kg. afterwards,
The ingot was pulverized by the water atomizing method. The chemical composition of these powders is shown in Table 1. Using injection molding metallurgy of these powders, plate thickness: 3 mm × parallel part width: 4 mm × grip part width: 1
6 mm x total length: Sintered into a test piece material with dimensions of 80 mm.
Using this test piece, a tensile test and a creep rupture test with an applied load of 38.0 kgf / mm ² were carried out in an atmosphere of air at a heating temperature of 600 ° C. The results are also shown in Table 1.

[Effect of the Invention] The alloy for injection molding powder metallurgy of the present invention is extremely excellent in high temperature strength as compared with the conventional alloys for injection molding powder metallurgy. Therefore, the injection-molded powder metallurgy member can be applied to, for example, a gas turbine high-temperature component requiring high-temperature strength, and its industrial value is very large.

Claims (1)

(57) [Claims] 1. C: 0.2 to 0.6, Cr: 15 to 25, Ni: 15 in% by weight.
-25, Co: 15-30, Mo: 5-15, W: 1-8, Nb: 1-8, and the rest having a composition of Fe and inevitable impurities. High strength heat resistant alloy for injection molding powder metallurgy.