Effects of Laser Power on Track Profile and Structure Formation during Selective Laser Melting of CoCrMo Alloy

A strong research effort has continued to determine how selective laser melting (SLM) process parameters relate to the amount of defects present in SLM products. However, how these parameters affect the track profiles which should geometrically affect the amount of lack of fusion (LOF) during SLM has not been studied. This study is needed as severe LOF should be a severe quality and property issue. In this work, how laser power ( P ) and thus energy, as other build rate related parameters are kept unchanged, affects the size of SLM tracks and the formation of LOF during SLM of CoCrMo alloy has been studied. Through examining the track profiles, track sizes have been geometrically demonstrated to insufficiently overlay and overlap for LOF free when the recommended condition ( P = 180W) was used. A further contributing factor for LOF is the irregularity of track shape. Increasing P increased the sizes and improved the stability of the melt and the shape regularity of the tracks, reducing the amount of LOF. It will be shown that there is a rapid decay in the amount of LOF as P increases from 180 W, predominantly as the result of geometrical effect of the track profile on track coverage.