Powder melting efficiency during laser powder bed fusion of stainless steel and titanium alloy

In the laser powder bed fusion (LPBF) process, powders exhibit different behaviors based on process conditions and material properties. Some powders may melt and form deposits, others become partially melted and attach to the melt pool, while some may be ejected, and certain powders remain unaffected. However, only a fraction of powders ultimately undergo full melting and contribute to the formation of the final parts. Here, we define powder melting efficiency as the ratio of the deposited track mass to the mass of powder consumed. We investigate the influence of process parameters and alloy properties on powder melting efficiency using stainless steel 316 and Ti6Al4V powders. We find that with rising laser power or decreasing scanning speed, the deposited track width increases at a greater rate than that of the denudation width. Therefore, powder melting efficiency can be improved by increasing laser power or reducing scanning speed and layer thickness. Under the same process condition, Ti6Al4V alloy exhibits higher powder melting efficiency compared to stainless steel 316. Multiple powder melting efficiency maps are generated under various process conditions for two alloys. In addition, we derive a dimensionless powder melting index to represent the ratio of the volumetric energy input to the energy required to melt per unit mass powder. This well-tested dimensionless index provides the quantitative correlation among the process parameters, alloy properties, and powder melting efficiency. Both the powder melting efficiency maps and dimensionless index can help optimize process conditions for printing high-quality parts economically.