Micro-morphology And Formability Of Stainless Steel Components Produced By Selective Laser Melting

Selective Laser Melting(SLM) is a new method of direct forming metal parts, which is the combination of Rapid Prototyping and Laser Cladding. It has great advantage on producing metal parts with small sizes, high accuracy, low surface roughness and complex structures, which has widely industrial applications prospect. But the lack of fundamental research on parameters optimization retards the applications of this advanced technology. In this dissertation, laying powder process, single-pass laser cladding, multi-track overlapped laser cladding, thin walls and blocks have been studied to optimize the process parameters by SLM.In this dissertation, the effects of the main process parameters including laser energy density, laser power, laser scanning speed, layer thickness and overlapping rate etc. on the quality of parts by SLM has been studied. The results show that laser energy density is the most important parameter to determine the quality of the coatings. The critical value of 2.7J/mm2 is necessary to assure the good formability, below which there will be no single-pass laser cladding. Enhancing the laser energy density by increasing laser power is more useful than decreasing scanning speed to obtain good formation quality.The height, width and dilution rate of laser cladding tracks are decided by SLM process parameters. The value of dilution rate can be used to analyze the formation quality quantitatively. No defects can be observed in the parts when the dilution rate is bigger than 50%, whilst few defects can be found when the dilution rate is bigger than 20%. The relationships between the process parameters and the surface quality during forming multi-tracks and thin walls were studied by the use of sample variance analysis method. The process parameters to forming blocks have been optimized according to multi-track overlapping laser cladding.Finally, several solid parts with well-distributed micro-hardness were rapidly produced by SLM with the layer thickness 0.2mm, laser power 150W, scanning speed 24m/min and the overlapping rate 33%. The phase of powder materials keeps unchanged after laser melting.