Fabrication of functionally gradient materials in inconel/steel system by laser beam

Abstract

Laser surface-alloying method was applied in order to develop functional gradient Inconel/Steel alloy material. Inconel 690 sheet was placed on a steel substrate, and then a series of high power CO2 laser beams was irradiated in order to make a homogeneous alloyed layer. Simultaneous compositional gradients of two different kinds of alloying elements (Cr and Ni) were investigated in this material, and experimental values were compared with the calculated values. In order to determine the microstructure, phase and composition of each alloyed layer, SEM, XRD and EDS were used. Sequential repetition of laser surface-alloying treatments up to 4 times resulted in about 3 mm layers of fair compositional gradients from 21%, 40% and 39% to 0%, 0% and 99% for Cr, Ni and Fe in this material. Since volume changes were different between the alloyed region and the heat-affected substrate region, oblique cracks were formed at the far side of the boundary region.