Influence of spatter particles contamination on densification behavior and tensile properties of CoCrW manufactured by selective laser melting

Abstract Due to spattering particles forming during Selective Laser Melting, powder pollution may severely affect the quality of the fabricated components and cause defects inside the microstructure to degrade the mechanical properties. Therefore, investigations into the change in powder characteristics and related microstructure defects, tensile properties are needed. In this paper, the influence of powder re-using time on Selective Laser Melting-based fabrication of CoCrW alloy was studied. The spattering process and the powder pollution caused by spatter particles were observed via high-speed imaging. The densification mechanism and the evolution of the microstructure of the CoCrW printed components were analyzed. The mechanical properties of the components printed using powders polluted at a varying degree by the spatter were tested at different stages of the life cycle. Results indicate that the Selective Laser Melting-generated spatter particles look more complex than the virgin powder particles. Compared with laser irradiating on the substrate, much more spatter escaped from the molten pool as the laser irradiated on the powder; the powder showed a trend towards increased particle size diameter through repeated recycling; residual pores distribution state and size applied with the various powder usage times were analyzed, pores with the average size of 300 μm could be achieved when powder recycled for the sixth time. At last, it is concluded that the spatter severely affects the mechanical properties of the fabricated components, as the tensile strength, yield strength and elongation of CoCrW alloy was reduced from 1284 MPa, 855 MPa and 11.15% to 874 MPa, 689 MPa and 3.82%, respectively. This gives insights into the influence of powder features on Selective Laser Melting-fabricated components and into improvement in stability of Selective Laser Melting manufacturing processes by controlling spatter formation.