Research Die-casting Mold Surface Laser Processing Parameters Optimization

Die casting die as the most important parts of die casting process. In the productionprocess, on the one hand, suffered directly scour,wear and high temperature of metal liquidoxygen, on the other hand, suffered the hot and cold cycles by the hot metal heating andcooling medium (water, oil, air),over and over again. Result in die casting dies easy toproduce fatigue cracks.In recent years, by means of surface modification technology, especially using the laserstrengthening technology to improve the service life of the mold had obtained very idealeffect.This paper take H13steel and Dievar steel as the research object to improve the thermalfatigue resistance, wear resistance of die casting die.Using laser rapid fused technologyprocessed biomimetic laser-remelting unit on the surface of H13steel and Dievar steelThe influence law between the laser process parameters with the morphology andmicrostructure of laser-remelting unit were analyzed by using optical microscopy(OM),scanning electron microscopy(SEM)and energy spectrometer(EDS). The hardness of lasermelted zone was also investigated by microhardness tester,thermal fatigue properties of thelaser fused materials was researched by use of high frequency heating thermal fatigue testingmachine.The result showed that：1) Microstructure of biomimetic laser-remelting unit of H13and Dievar was composedof cryptocrystalline martensite and a small amount of residual austenite, grain refining, alloyelements distributed uniformly and microhardness increases significantly.2) With the increase of current and pulse, the width of biomimetic laser-remelting unit isbasically linear increasing trend. The unit-width increased obviously before7Hz of frequencyand then gently. The unit-width decreases with the increase of defocusing which ranges from-3mm to+3mm.Then the unit width has increasing trend after+3mm. Defocusing effect onthe unit of the most significant, the order of influence on the unit width by differentparameters was defocuing> frequency> current> pulse3) Laser bionic fused samples after2500times thermal fatigue cycle, its thermal fatiguecracks initiation time was postponed obviously, cracks extension rate reduced substantially.When the fatigue cracks propagated to the biomimetic laser-remelting unit,we found the fatigue crack extension stagnated or the direction deflection.