MODIFIED NICKEL-CHROMIUM-IRON-ALUMINIUM ALLOY

摘要

An oxidation-resistant alloy for use in a high-temperature or thermal cycling environment. The alloy comprises a nickel-based matrix having a solid solution of 19-23 % chromium and 3-6 % aluminum. A self-healing, thermodynamically stable oxide layer is formed upon a surface of the alloy which is exposed to an oxidizing atmosphere over a range of temperatures for extended periods of time. The oxide layer protects the alloy from the oxidizing atmosphere. Additions of calcium and yttrium are made to the matrix to substantially remove or stabilize oxygen and sulfur dissolved in the molten alloy. These additions result in retention of about 0.01-0.04 % of calcium and 0.01-0.04 % yttrium in the cast alloy. The matrix further includes about 2-8 % iron to inhibit nucleation and growth of a "gamma prime" nickel aluminium intermetallic compound which would otherwise adversely harden the alloy and cause local disturbance of a uniform distribution of aluminium.