Investigation On Process Of Laser Micro Sintering 316L Stainless Steel

The micro metal parts are widely utilized in many industrial field, and laser micro sintering(LMS) technology is promise for fabricating this kind of metal parts rapidly. This thesis investigated laser micro sintering process of 316 L stainless steel systematically, and some value results have been obtained. The main research contents and results are as follows:(1) Firstly, the influence of average laser power and scanning speed on the morphology of single track have been investigated. The results show that the large average laser power and low scanning speed lead to a grooving scanned track, and the low average laser power and high scanning speed lead to a discontinues scanned track. The continuous single scanned track with good morphology can be obtained if using suitable average laser power and scanning speed. The process window of single scanned track with pulse frequency of 200 kHz, the average laser power of 40~90 %, the scanning speed of 100~1000 mm/s and accumulated energy density range from 2.21×106 to 3.95×106 W/mm2 is obtained by comprehensively analyzing the surface morphology, the cross-sectional shape and width of scanned track.(2) Secondly, the influence of the process parameters, such as average laser power, scanning speed, layer thickness, hatching space and scanning strategy on the relative density of fabricated parts has also been investigated. The results show that a high relative density can be obtained if the accumulated volume energy density in the range of 2.1×107 to 4.9×107 W/mm3. Finally, the spatter in laser micro sintering was analyzed, and some methods for improvement were proposed.(3) Lastly, the microstructure and properties of laser micro sintering 316 L stainless steel have been studied. The scanning speed and hatching space have a significant effect on the surface roughness of the fabricated parts. The optimal surface roughness Ra is 3.53 μm. The microstructure consists of columnar grains. The scanning speed has effect on the form of the columnar grains. The main microstructure is cellular grains when the scanning speed is low, and the main microstructure are dendrite and cellular grains when the scanning speed is high. The phase of sintered samples is austenite. The ultimate compressive strength of sintered samples is 1305.93 MPa.