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

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 mu m to nanoscale (similar to 80 nm). Matrix transformed from austenite to ferrite when addition of Al was >4.72%. Oxidation resistance of samples containing 4.72% Al 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 4.72% Al performed similar to 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 4.72% Al performed the optimal combination properties.