Experimental investigation of nanosecond pulsed Nd:YAG laser re-melted pre-placed powder beds

Describes the effects of the major process variables Q-switch pulse frequency, laser power, scan speed, scan spacing and scan length) on the production of single layer coupons. Results are compiled as a list of qualitative effects on the samples, such as degree of melting, shock compression effects, thermal stress cracking, etc. The results show that at certain pulse frequencies, evaporation recoil forces overcome the surface tension forces acting on the melt, improving cohesion compared to continuous wave (CW) lasing regime. The advantages lie in greater scan spacing and scan speeds enabling faster processing times for metallic objects built in this manner. The results also show the effect of power, scan speed, scan spacing and scan length on the morphology of the samples.