Study On Laser Surface Treatment Of AISI301Stainless Steel

In the paper we use CO2laser device to do the local laser surface treatment incold-rolled and annealed301stainless steel. And study on the microstructure andmechanical properties of301stainless steel after the laser cycle irradiation by using theoptical metallographic microscope, scanning electron microscope (SEM), transmissionelectron microscope (TEM), X-ray diffraction analysis, hardness test and other modernanalysis means. The experimental results show that it is the thermal stress causes plasticdeformations, and the deformations lead to martensite phase transformation happenedafter laser surface treatment in annealed301stainless steel. After laser surface treatment of750℃×200cycles, lath martensite can be obtained, and the laser surface treatment of750℃×200cycles and850℃×300cycles have the same effect in annealed301stainlesssteel. After laser surface treatment of850℃×300cycles,the depth of hardening layer isabout800μm. Laser surface treatment can cause certain preferred orientations. with theincrease of loop cycles and treatment temperatures, the dislocation density, the microstrain,the content of martensite and the stacking fault probability all have a significant increase,but the microcrystalline dimension has a significant decrease in annealed301stainlesssteel. Strain strengthening, fine-grained strengthening and phase transforming are threemain factors which lead to the increase of hardness in annealed301stainless steel. Aftercold rolling of301stainless steel, the more the rolling reduction is, the larger martensitepercents are. When rolling reduction is92%, the percentage of martensite is96.5%. Ofcourse, martensite can lead to the increase of hardness.301stainless steel whose collingreduction is92%can happen the reversal transformation of martensite after the lasersurface treatment, then tiny and equal axial and hybrid organizations can be obtained, andthe average grain size is about38nm. With the increase of loop cycles and treatmenttemperatures, more of the reversal transformation of martensite happened in301stainlesssteel which is cold-rolled state, and hardness will decrease in the process. Temperature ismore effective to the reversal transformation of martensite than loop cycles in cold-rolled301stainless steel.