Additive manufacturing of a functionally graded material from Inconel625 to Ti6Al4V by laser synchronous preheating

This work examines a functionally graded material, fabricated by directed energy deposition additive manufacturing and laser synchronous preheating that grades from Inconel625 to Ti6Al4V. The microstructure evolution, cracking behavior, phase characteristics and microhardness were determined as a function of position within the graded material. The cracks occurred in the transition zone between 80% Inconel625 + 20% Ti6Al4V and 70% Inconel625 + 30% Ti6Al4V for the non-preheated sample due to the formation of massive Cr- and Moenrich phases, while no cracks were found in preheated gradient samples. A series of phase evolutions with the increase of Ti6Al4V occurred: gamma, gamma + Ni3Ti, Ti2Ni + TiNi + beta-Ti, beta-Ti + Ti2Ni, alpha-Ti + beta-Ti + Ti2Ni, alpha-Ti + beta-Ti. The maximal hardness obtainable in the 60% Inconel625 and 40% Ti6Al4V deposition layer is determined largely regarding the presence of the various phases. Laser synchronous preheating was an effective measure on improving deposition and crack suppression in laser deposition for Inconel625/Ti6Al4V graded material.