Microstructural and properties evolution of austenitic heat resistant steel after addition of aluminium

Abstract

Effect of aluminium on microstructure and properties of austenitic heat resistant steel was investigated. The results showed that Al addition led to formation of spheroidal and dispersed Ni₃Al. After solution treatment, Ni₃Al particles experienced a significant refinement from 1·5 μm to nanoscale (∼80 nm). Matrix transformed from austenite to ferrite when addition of Al was >4·72. Oxidation resistance of samples containing 4·72Al was two times higher than Al free samples due to the formation of compacted Al₂O₃ scales. Excessive Al resulted in the formation of Al₃Fe₅O₁₂ and AlN on oxidation surface, which destroyed the oxidation resistance. Dispersedly precipitated Ni₃Al effectively supported the matrix and enhanced the wear resistance, and samples containing 4·72Al performed ∼80 higher in wear resistance than Al free samples. Al significantly improved the microstructure and the properties of austenitic heat resistant steel, and samples containing 4·72Al performed the optimal combination properties.