Effect of Number of Remelting Times on Surface Quality and Wear Performance of 316L Produced by Selective Laser Melting
The number of remelting times(NRM)significantly influences the surface roughness and wear resistance of components used in selective laser-melting(SLM)additive manufacturing.Therefore,the investigation of its influencing mechanism and the determination of an economical NRM are crucial for applications of SLM additive manufacturing technology.In this paper,316 L specimens were prepared using an SLM additive manufacturing device,during which they were grouped and remelted by a laser 0-3 times.Subsequently,the surfaces of the remelted specimens were characterized using a three-dimensional profile scanner and a scanning electron microscope.Furthermore,friction and wear experiments were conducted on the specimens using a high-speed reciprocating friction and wear testing machine,and the masses before and after wearing were measured using an electronic analytical balance.The following beneficial findings were observed.The surface roughness of the components in SLM additive manufacturing decreased with an increase in NRM.Specifically,the values of average surface roughness Sa,Sq,Sv,and Sz decreased from 8.437,11.88,82.68,and 252.2 μm(normal printing without remelting)to 6.18,7.735,37.597,and 104.36 μm(after remelting for three times)by 26.75％,34.89％,54.53％,and 58.62％,respectively.The average friction coefficient increased gradually,whereas the mass wear decreased with an increase in NRM.For the specimens remelted two and three times,the instantaneous maximum friction coefficient was greater than 1 in the later stage of the wear experiment.This is attributed to the fact that after multiple remelting times,the surface of each sample becomes very clean,resulting in very close contact between the friction pairs.Moreover,"contact growth"occurs prior to significant sliding,and the frictional force exceeds the positive pressure because of the constantly increasing contact area.These changes in surface roughness and wear performance can be explained as follows.Each remelting process further melts and sinks the welding marks and particles adsorbed on the surface until they disappear.Consequently,the"peak-valley"phenomenon at the overlap of adjacent melt channels is suppressed,and defects such as pores and balls are gradually repaired.Eventually,the surface flattens.Furthermore,different NRMs resulted in varying degrees of variation in surface roughness and wear.Accordingly,this study innovatively proposes the concept of an economical NRM.The comprehensive change rates of the surface roughness and wear performance after one,two,and three remelting cycles were 26.61％,43.60％,and 23.68％,respectively,and the economical NRM was 2.Finally,application examples of the mining machinery of economical NRM based on the research results are presented.This study is expected to provide new clues for improving the surface quality and wear resistance of components in SLM additive manufacturing while reducing processing costs.Based on different requirements,NRM can be used for SLM additive manufacturing of parts on the surface or layer-by-layer inside.NRM can be used to improve the mechanical,metallurgical,and physical properties of additive manufacturing parts,thereby improving the properties of parts,such as wear resistance,corrosion resistance,and fatigue resistance.
SLM additive manufacturing316Lnumber of remelting timessurface roughnessquality wearfriction factor
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