| Laser polishing is a special processing technology with prospect of application, particularly used for processing of high hardness and size of the parts that conventional methods cannot deal with it. 38 CrMoAl has many superiorities including high surface hardness, high fatigue strength, good resistance to overheating resistance and widely used in mechanical machining, such as piston bolt and lathe spindles. By using laser polishing technology, 38 CrMoAl can be polished in an efficient and green way.In this work, 38 CrMoAl was mainly polished by excimer laser(248 nm). The effects on surface roughness of 38 CrMoAl steel were analyzed by a three-dimensional topography instrument. Based on the surface morphology characteristics before and after polishing, we analyzed the impact of pulse count, defocusing amount, pulse repetition rate, laser energy and different pre grinding conditions. And observe the re-melting depth of excimer laser and semiconductor laser irradiation on 38 CrMoAl by SEM. We obtained better processing parameters. Those are the position where is above the laser focal plane 1.4 mm, the laser energy of 300 mJ, 8 Hz pulse repetition rate and 5 pulses. By using the micro-polishing method, the roughness of the metal surface could be decreased from 123.70 nm to 74.96 nm, decrease of 39.4%.Secondary, 38 CrMoAl was polished by YAG laser(1064 nm). Based on the surface morphology characteristics before and after polishing, we analyzed the impact of laser voltage, pulse duration, defocusing amount and apertures. we obtained better processing parameters with a 4-hole apertures, the position where is above the laser focal plane 3mm, the voltage of 790 V and 0.17 ms pulse duration. By using the micro-polishing method, the roughness of the metal surface could be decreased from 142.02 nm to 79.10 nm, decrease of 44.3%.The experimental results show that, the excimer laser can be more rapid and effective for 38 CrMoAl polishing to reduce the surface roughness without heat effect. |
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