Recent Developments in Laser Melt/Particle Injection Processing

Investigations into crack formation in particle injected surfaces and into microstructural evolution during cladding were some of the recent developments in laser melt/particle injection processing. Both surface modification techniques involved blowing powder particles into a melt pool formed by a laser beam. When the particulate materials were metal carbides composite surface layers were formed and the thermal stresses that developed during cooling of the carbide injected layer resulted in the formation of microcracks. It was found that modest levels of preheating were sufficient to prevent cracking and that cracking was eliminated mainly by the reduction in thermal stresses and not by modifications in microstructure. With lower melting alloy powders clad overlays were formed. It was found that the limited mixing between the clad material and the substrate resulted in complex macrostructures containing fluid-flow driven segregation bands. The degree of microstructural in-homogeneity depended upon the type of substrate material and had a direct influence on the soundness of the cladding.