Temperature and distortion in laser melt injection of MMC wear-resistant coatings in a copper beryllium alloy

Abstract

Abstract Wear-resistant coatings made of MMC materials (metal matrix composites) are ideal for increasing the service life of tools subjected to high abrasive stresses. Such MMC surfaces can be produced by laser melt injection during the manufacturing process of the tools or subsequently as a retrofit near-net-shape. However, during laser melt injection (LMI) thermally induced residual stresses can be introduced into the MMC surfaces. These can have a detrimental effect on the service life of these surfaces and thus reduce the positive effect of wear resistance. In order to determine the influence hard particles injected during LMI have on residual stresses within the surface layer the distortion of the surface layer was evaluated. MMC layers consisting of a copper beryllium matrix and fused tungsten carbide hard particles were created by LMI. The MMC layers are compared to parts with remelted surfaces. Laser power and process velocity were varied to examine their influence on distortion. The process temperature was recorded on the melt pool by a two-color pyrometer. After the process the top layer of the MMC surface was cut off by wire EDM and then measured with a coordinate measuring machine. It is shown that an increase of incorporated powder mass per unit length and process temperature lead to higher distortions.