Superalloy with oxide dispersion hardening having improved corrosion resistance and based on nickel

TECHNICAL FIELD 
Superalloys with oxide dispersion hardening based on nickel which, owing to 
their outstanding mechanical properties at high temperatures, find 
application in the construction of heat engines subjected to high thermal 
and mechanical loads. Preferred application as blade material for gas 
turbines. 
The invention relates to the further development of nickel-based 
superalloys with oxide dispersion hardening having completely ideal 
properties in relation to high-temperature strength, long-term stability 
and resistance to oxidation and corrosion in an aggressive atmosphere. 
It relates in particular to a superalloy with oxide dispersion hardening 
having improved corrosion resistance and based on nickel. 
Prior art 
The following references are cited in relation to the prior art: 
G. H. Gessinger, Powder Metallurgy of Superalloys, Butterworths, London, 
1984; 
R. F. Singer and E. Arzt, to be published in: Conf. Proc. "High Temperature 
Materials for Gas Turbines", Liege, Belgium, October 1986, 
J. S. Benjamin, Metall. Trans., 1970, 1, 2943-2951. 
In the course of recent years a new class of high-temperature superalloys, 
intended in particular as components of heat engines (gas turbine blades) 
has been developed. These are nickel-based alloys which contain finely 
divided dispersoids in the form of oxides. Mostly, the latter are Y.sub.2 
O.sub.3 particles. One of the most well-known alloys of this type with 
oxide dispersion hardening is the nickel-based alloy obtainable from INCO 
under the trade name MA 6000 which has the following composition: 
Cr=15.0% by weight, 
Al=4.5% by weight, 
Ti=2.5% by weight, 
Mo=2.0% by weight, 
N=4.0% by weight, 
Ta=2.0% by weight, 
Zr=0.15% by weight, 
8=0.01% by weight, 
C=0.05% by weight, 
Y.sub.2 O.sub.3 =1.1% by weight, 
Ni=Remainder. 
(cf. H. F. Merrick, L. R. Curwick and Y. G. Kim, Nasa Report CR-1335150, 
Contract NAS-3-19694, 1977, Cleveland, Ohio, USA and R. C. Benn, L. R. 
Curwick and G. A. J. Hack, Powder Met. 1981, No. 4, pages 191-195). 
Although said alloy has excellent mechanical properties at high 
temperatures, in numerous applications it fails to meet the operating 
requirements in terms of oxidation and sulfidation resistance. 
In order to improve the anticorrosion properties, INCO have developed a new 
alloy. It has the following composition: 
Cr=20.0% by weight, 
Al=6.0% by weight, 
Mo=2.0% by weight, 
W=3.5% by weight, 
Zr=0.19% by weight, 
B=0.01% by weight, 
C=0.05% by weight, 
Y.sub.2 O.sub.3 =1.1% by weight, 
Ni=Remainder. 
Although this alloy, which has higher Cr and Al contents than MA 6000, has 
improved corrosion resistance, as a result of the formation of brittle 
phases in certain temperature ranges it has a tendency to instability 
phenomena which impair the mechanical properties.