THE EFFECT OF ALUMINUM CONTENT ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF HEAT RESISTANT STAINLESS STEEL GX40CRNISI22-10

Abstract

This study investigates the influence of increasing aluminum content on the microstructure evolution and mechanical properties of GX40CrNiSi22-10 heat-resistant austenitic stainless steel. Four grades of this steel were prepared with aluminum (Al) contents of: 0.3%, 0.77%, 1.19%, and 1.85%. The microstructure was inspected and mechanical tests were performed at room temperature. The results showed that the microstructure of the first three steels is entirely austenitic with precipitation of chromium carbide at the grain boundaries and in the austenitic matrix, while the microstructure of the fourth steel is duplex due to the formation of ferrite islands with precipitation of chromium carbides at the phase boundaries and in the austenitic matrix. The highest tensile strength is achieved in the steel containing 1.85% Al, while optimal ductility, characterized by a fracture elongation of about 34.7%, is obtained in the steel with 1.19% Al. This improvement in ductility can be attributed to the dispersed precipitation of aluminum nitrides (AlN) in the austenitic matrix and the fine discontinuous precipitation of chromium carbide.