Effect of additive and subtractive hybrid manufacturing process on the surface quality of 18Ni300 maraging steel

The effect of process parameters on the surface quality of 18Ni300 maraging steel formed by selective laser melting (SLM) was investigated. Surface modification of SLM specimens was performed using milling as a subtraction method to investigate the effect of milling process parameters on the surface quality of SLM specimens. Comparing and analyzing the surface quality after additive and subtractive processes, the results show that the increase of laser power during SLM can improve the surface morphology, but there is always a balling effect. The surface quality deteriorates when the scanning speed increases. When the laser power increases or the scanning speed decreases, the microhardness increases and the error decreases. The residual stress does not vary linearly with the change of laser power or scanning speed, and the scanning speed has a greater effect on the residual stress than the laser power. The best surface quality was achieved with a laser power of 180 W and a scanning speed of 300 mm s(-1). The laser power and scanning speed did not significantly affect the microstructure of the SLM-formed specimens. In the milling process, an increase in the feed rate will make the surface quality worse, and an increase in the cutting speed will make the surface quality better. The best surface quality was obtained with a cutting speed of 10 m min(-1) and a feed rate of 36 mm min(-1). The grain refinement effect is weakened when the feed rate is increased, and the grain refinement effect is enhanced when the cutting speed is increased. The surface quality of SLM-formed maraging steel specimens improved somewhat after milling.