Laser rapid forming of SS316L/Rene88DT graded material

The stainless steel-SS316L/superalloy-Rene88DT graded material was successfully fabricated using laser rapid forming. A linear compositional gradient, from 100% SS316L stainless steel to 100% Rene88DT superalloy, was achieved within a thickness of 40mm of laser multilayer deposition. The solidification behavior and the morphological evolution along the compositional gradient were investigated. It was found that, in the gradient zone, within the processing parameters of this study, there was continued epitaxial growth of the gamma phase of the columnar dendrites, starting with 100% SS316L stainless steel to 100% Rene88DT superalloy, with the <100> crystallographic orientation parallel to the gradient direction. Clad layer bandings were found in the samples; however, the continuity of the growth of the columnar dendrites was not upset. The results are explained by the columnar to equiaxed transition theory and the criteria for planar interface instability and dendritic growth. (C) 2004 Elsevier B.V. All rights reserved.