Heat-resistant Ni-alloy material excellent in resistance to oxidation at high temperature

摘要

A composite resistive to high-temperature corrosion and abnormal oxidization, maintains original excellent high-temperature characteristics of Ni alloys over a long period of time, and suitable for applications in a high-temperature such as gas turbines, jet engines, and elements for exhaust-gas systems. A heat-resistant Ni-alloy composite has excellent high-temperature oxidation resistance, including a Ni-alloy substrate that has been subjected to an Al-diffusing treatment. The surface coat has a multi-layer structure including an inner layer composed of an alpha-Cr phase and an outer layer composed of a beta phase (Ni-Al-Cr) and a gamma' phase (Ni₃Al(Cr)) on the substrate surface. The Al content in the outer layer is at least 20 atomic percent. The alpha-Cr phase functions as a diffusion-barrier layer. The outer layer retains and secures a high Al content required for self-regeneration of a defective portion of the Al₂O₃ layer damaged in an operating condition.