Wear resistant alloy for high temprature applications

Abstract

Low cost alloys resistant to mechanical requirements related to high temperatures, resistant to corrosion, resistant to abrasion, with high workability and which meet different requirements in the conditions for application in either exhaust or intake valves for internal combustion engines. The main features of the alloys is the precipitation of Ni3Nb and niobium carbides in its microstructure. In percentage, its mass consists of: 0.15 to 0.50% C, up to 3.0% Mn, up to 1.0% Si, 12.0 to 25.0% Cr, 25.0 to 49.0% Ni, up to 0.50% Mo, up to 0.50% W, up to 0.50% V, 0.50 to 5.0% Cu, 1.85 to 3.0% Al, 1.0 to 4.5% Ti, 3.1 to 8.0% Nb, 0.001 to 0.02% B, 0.001 to 0.10% Zr, up to 2.0% Co, where (Ni+Co) is not higher than 50.0% in mass, nor lower than 25% in mass. The rest is made of iron and impurities inevitable to the Alloy manufacture procedure.

Description

[0001]This application claims benefit of provisional application 60 / 924,973, filed Jun. 7, 2007.FIELD OF INVENTION[0002]This invention deals with an Ni—Fe—Cr precipitation hardened superalloy for application in internal combustion engine valves, having as chief characteristics the precipitation of Ni3(Al,Ti,Nb) and niobium and titanium carbides in its microstructure. The alloy project, based on its microstructure aspects, allows for the alloy hereof to be provided with properties equal to or higher than those of the alloys used in internal combustion engine valves, associated with the alloy's significant cost reduction because of the lower nickel content.[0003]The alloy hereof is intended for valves' manufacture, where the alloy is required to have several properties, among them the following: oxidation resistance, wear resistance and heat resistance, because of the high temperatures used in the application.BACKGROUND OF THE INVENTION[0004]Conventionally, the materials used for exha...

AI Technical Summary

Benefits of technology

[0011]Another element used by this invention in higher quantities than the state-of-the-art alloys is aluminum, which has a prevailing function of coherent intermetallic containing niobium, Ni3(Al,Nb), thus improving the material's heat resistance. Additionally, aluminum improves the alloy hot oxidation resistance.

[0031]The reduced total titanium percentage in the alloy by the niobium addition in quantities higher than 3.5% improves its hot workability, since the alloy's hot ductility is threatened to values above 4.0% for the sum of titanium and aluminum contents (Ti+Al).

Problems solved by technology

Such extreme stresses in terms of mechanical resistance and corrosion resistance at high temperatures require the use of costly nickel-based superalloys.

Many alloys are coated with Stellite (cobalt base alloy) on the valve's hardfacing, which also increases the final cost of the valve.

One example of an excellent performance alloy in these applications is the NCF 751 alloy, which is very costly because of its high nickel content, above 70%.

Images