Austenitic heat-resistant nickel-base alloy

Abstract

Austentic heat-resistant nickel-base alloy comprising (in % by mass) 0.03-0.1% of C, 28-32% of Cr, 0.01-<0.5% of Mn, 0.01-<0.3% of Si, 0.01-<1.0% of Mo, 2.5-3.2% of Ti, 0.01-<0.5% of Nb, 0.01-<0.5% of Cu, 0.05-<2.0% of Fe, 0.7-1.0% of Al, 0.001-<0.03% of Mg, 0.01-<1.0% of Co, 0.01-0.10% of Hf, 0.01-0.10% of Zr, 0.002-0.02% of B, 0.001-0.01% of N, max. 0.01% of 5, max. 0.005% of Pb, max. 0.0005% of Bi, max. 0.01% of Ag, balance Ni and minor components due to the production method, where the sum of Ti +Al is from 3.3 to 4.3%, the sum of C+(10×B) is from 0.05 to 0.2%, the sum of Hf+Zr is from 0.05 to 0.15%, the Ti / Al ratio is >3 and Zr / Hf is 0.1 to 0.5.

Description

[0001]The invention relates to an austenitic heat-resistant nickel-based alloy.BACKGROUND OF THE INVENTION[0002]In the “Proceedings” for Diesel Engine Combustion Chamber Materials for Heavy Fuel Operation, 1990, the Institute of Marine Engineers provides a summary of the current prior art and the intensive research and development that has been performed in the preceding years in the field of valve materials. According to this, primarily Alloy 80 A, having (in mass %) 0.08% C, 19.5% Cr, 75% Ni, 1.4% Al, and 2.4% Ti has established itself for this application.[0003]In some cases Alloy 81, having (in mass %) 0.5% C, 30% Cr, 66% Ni, 0.9% Al, and 1.8% Ti was also used. Occasionally these alloys are used for basic materials for valves, the valve seat section also being coated with a wear-resistant material as is described for instance in EP-B 0521821. This publication provides the chemical composition for the basic material as follows (in mass %): 0.04-0.10% C, ≦1.0% Si, s 0.2% Cu, ≦1.0%...

AI Technical Summary

Benefits of technology

[0004]At the current usage temperatures of less than 750° C., Alloy 80 A was distinguished by a longer service life in LCF trials and better wear resistance, while, due to its better corrosion resistance, Alloy 81 was tested under conditions like those that would be encountered for instance in diesel engines for ships. Each of these alloys has i

Problems solved by technology

Each of these alloys has its particular advantages, but neither satisfies all of the requirements for mechanical and corrosive properties.

A remedy using an additional coating involves additional undesired production and material costs.

Powder metallurgical production is also unfavorable from a cost standpoint.

But this alloy does not provide adequate hot corrosion resistance, either.

In addition, there is the fact that future more powerful engines, such as diesel ship engines, will be operated at temperatures up to about 850° C., which also places high demands on the valve material, especially when the service life is to be maintained and no additional maintenance work is desired.