Effect Of Pulse Overlap On Surface Roughness And Microhardness In Laser Processing Of 316L Stainless Steel

Roughness is a very important surface property of materials. In order to study the effect of pulse overlap on the size of micro-dimples, micro-dimples were textured onto sample surfaces by ultra-fast pulsed laser and the dimple overlap was calculated according to the actual measured size of the dimples. On the basis of this dimple overlap, its influence on surface roughness and micro-hardness of laser textured micro-dimple surfaces of 316 L stainless steel was systematically investigated. The results show that the procedure of dimple overlap is influential on Ra and can be divided into 3 stages with different dominant factors. At the same time, dimple overlap has significant effect on micro-hardness. The detailed contents are as follows;(1) The spacing between the spots(in the X direction) and the scan lines(in the Y direction) was set to be equal. These two variables(pulse overlap and scan line overlap) were unified into one variable(scanning overlap).(2) Study of the surface damage mechanism on stainless steel with ultra-fast(u-f) laser pulses and the mechanism for the evolution of surface roughness. The effect of u-f pulse laser induced overlap on the surface roughness and the resultant performance of metals was analyzed.(3) Laser pulses with different scanning overlap were used to process the surface of stainless steel to find how micro-hardness might correspond with overlap and to determine the overlap conditions to maximise micro-hardness. Proposed reasons for the increase of micro-hardness on the surface of stainless steel were found by interpretation of analysis by X-Ray Diffraction and SEM for compositional and morphological properties, respectively.(4) Samples with different scanning overlap were used to test the corrosion resistance of the stainless steel surface by the Zennium ZAHNER electrochemical workstation. The corrosion resistances of samples with different scanning overlap were compared to the X-Ray Diffraction compositional, and SEM morphological, analyses along with electrochemical circuit simulation in order to hypothesise an appropriate mechanism.