Additive fabrication of 316L/Inconel625/Ti6Al4V functionally graded materials by laser synchronous preheating

Abstract

This work examines a functionally graded material, fabricated using laser-directed deposition and synchronous preheating, that grades from 316L stainless steel to Ti6Al4V through a transition of Inconel625. The cracking behavior, microstructure evolution, and microhardness were determined as a function of position within the graded materials. The results showed that cracks occurred in the 316L/Inconel625- and Inconel625/Ti6Al4V-graded specimen with no preheating, defined as a solidification crack and cold crack, respectively. Precipitations of Mo-enriched eutectic phase were experimentally identified to be the major cause of the cracking. The precipitated phases of prepared gradient materials were fine and uniform by laser synchronous preheating, and no cracks were found. The hardness reached the maximum value in 70% Inconel625 + 30% Ti6Al4V. Work shows that the key to fabricating 316L/Inconel625/Ti6Al4V gradient material by laser deposition is to reduce the formation of Cr and Mo enrichment phase and the uneven temperature tendency.