Effects of Nickel on Structure and Properties of Ferro Superalloy

Abstract

The affecting law of nickel on structure and properties of ferro superalloy, which was cast by intermediate frequency induction furnace, were studied by orthogonal experimental method. The tensile strength and oxidation weight gain rate at 1000°C were tested. The matrix microstructure and scale morphologies and composition were studied using scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. It was found that the high temperature tensile strength went up with the increase of nickel by the forming of high temperature strengthening phase of γ’. After 100 hours aging at 1000°C, γ’ phase separated in blocks. Certain content of nickel improved the high temperature oxidation resistance of test alloys, but excess of it caused the higher oxidation weight gain rate and loose structure oxide scales with holes and exfoliating. In considering of high temperature tensile strength and oxidation resistance, the ideal content of nickel in ferro superalloy should be 9wt.%, with which at 1000°C the tensile strength of test alloys mostly exceeded 70MPa, and the average oxidation weight gain rate was only 0.55g.m-2.h-1, reaching the strong oxidation resistance. Such scale was compounded by Cr2O3 and Fe(Ni)Cr2O4 with compact structure, fine and even oxide grains.