Affiliation:
1. Institute of Advanced Steels and Materials, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, China
2. School of Material Science and Engineering, Shanghai Institute of Technology, Shanghai, China
Abstract
A Ni–Co-base superalloy was subjected to three different pack aluminising procedures (1000 °C for 3.5 h, 890 °C for 8 h and 620 °C for 10 h) to produce the Al-rich coating with simultaneously improved oxidation and wear resistance. All samples showed a multi-layer coating made up of (Ni, Fe, Co)Al phase, (Ni, Fe, Co)3Al phase and transition layer. The AT620 sample possessed the lowest oxidation rate but the highest double-edge-notched (DEN) strain during high-temperature stress rupture. The high oxidation resistance might be associated with the creation of Al2O3 layer (∼5.6 μm), contributing to an inhibition of oxygen permeation. However, a premature failure was caused by the strong deformation incompatibility between the substrate and alumina layer. The AT890 samples had higher oxidation and creep-induced-crack resistance than those of the AT1000 samples, which was the result of the effective Al inter-diffusions in the transition layer suppressing the undesirable Cr-rich σ phase.
Subject
Materials Chemistry,Surfaces, Coatings and Films,Surfaces and Interfaces,Condensed Matter Physics