A NEW HIGH-TEMPERATURE, HIGH-STRENGTH AND CORROSION-RESISTANT NICKEL-BASE ALLOY FOR SERVICE TEMPERATURES UP TO 1200-DEGREES-C

The newly developed alloy Nicrofer 6025 HT has a creep strength R(m)/10 000 of 3.3 MPa at 1200-degrees-C achieved by a combination of solid solution hardening and carbide strengthening. These high amounts of carbon as well as chromium, titanium and zirconium support the formation of stable carbides which guarantee high creep strength even at the upper temperature limit. The excellent creep strength is combined with high oxidation resistance, because 2% aluminum in presence of about 25% chromium in the alloy are sufficient to provide for alumina scale formation, so that in cyclic oxidation tests performed in air a specific weight decrease of about 0,3 g/m2h even at 1200-degrees-C is not exceeded. The formation of an alumina scale results likewise in improved carburization resistance in CH4/H-2, because the aluminum oxide surface layer provides an effective protection against carbon pick up.