High-temperature oxidation behavior of mechanically alloyed Ni-based superalloys; Mechanical alloying ho ni yori sakuseishita sushu no Ni ki tainetsu gokin no koon sanka kyodo

Oxide dispersed and reinforced alloys developed by using the mechanical alloying (MA) method have excellent high-temperature strength and are used in harsh environments. Consequently, the alloys are demanded of extremely good oxidation resistance. This paper describes oxidation tests that apply thermal cycles from room temperature to 1273 K to several kinds of Ni-base heat resistant alloys fabricated by using the MA method and the hot isostatic pressing (HIP) treatment. The paper also mentions investigations on oxidation rates of alloys added with Fe, Al, Ti and Y2O3 and the structure of oxide films, and discussions on film generation processes. As a result, a number of findings was obtained, including the following results: the amount increase due to oxidation as a result of repeated oxidation in the atmosphere nearly follows the parabolic rate laws in each alloy; however, with N-1 (NNi-20Cr) alloy using Fe as an impurity had the oxide film peeled off and the amount increase due to oxidation increased; and the least oxidation amount increase was found in N-3 (NNi-20Cr-1.0Y2O3) alloy. 26 refs., 11 figs., 3 tabs.