Investigation Into Manufacturing Metal Parts Direct From Stainless Steel Powders Via Selective Laser Melting

Selective laser melting (SLM) is a new laser rapid manufacture technology. Its principle is to full melt the metal powder, and realized the rapid manufacture of metal parts based on the principle of delamination&adding. It can get metal parts of 100% density with the comparative machine performance to forging. SLM becomes the hotspot of rapid manufacture abroad now,but in our country it is in the first step. Now there are still two difficulty when manufacture industry parts by SLM. The first is there still some crack and hole in the part. The second is most of the SLM research in the world are to special metal powder, there still no commonness SLM study method is applicable for all the metal powder .To solve the two difficulties and directly manufacture metal parts by SLM, systemic research was taken to the density of SLM parts . The material researched was 316L stainlessness steel and 304L stainlessness steel. The purpose was to confirm commonness SLM study method at the same time of getting high density metal parts. The main research contents and results are as follows:(1) Established the commonness SLM study method for vary metal powders. Operated SLM experiment by 304L stainlessness steel powder. First fixed on the laser power,scan rate,scan line spacing,layer thick and scan road by line scan,surface scan and three-dimensional part scan. Then incised the three-dimensional part, measured the density by drainage method, and measured its microstructure,micro-hardness,strength. Finally we chose a set of parameter and got the part with high density and precision.(2) Optimized the processing parameters in selective laser melting of 316L stainless steel powder. Using crossing experiment to analyse the effect to part density and precision of various parameters selected such as laser power, scan speed, scan spacing.(3) The loose density of sphericity powder manufactured by gas atomization was higher than the powder manufactured by water atomization.First this is because the better liquidity.Second as to the same granularity, sphericity powder can get smaller layer thickness so the adjacent layer can compensate each other.In additon,the powder manufactured by gas atomization contained less oxygen,that will increase the wettability of the powder and make for high density parts.(4)The scan method was improved. Jump to change scan method can get smooth face,this will be benefit to the next layer shaped.After improved the powder and scan method finally got 95% density part by SLM.(5)SLM of other metal powder also researched.It can detect the influence of powder performance to SLM and provide the base for the SLM of such powders.(6)Composite process of SLM and Heat isostatic pressing (HIP) was studied preliminarily.