Surface Structure And Properties Of M2High Speed Steel After High Current Pulsed Electron Beam Treatment

In this study, the M2High Speed Steel W6Mo5Cr4V2was irradiated by High Current Pulsed Electron Beam (HCPEB) with different numbers of pulse and acceleration voltages. Metallographic microscope, SEM, XRD, EPMA, microhardness tester and wear tester were used to investigate the fundamental regularities of surface morphology and micro structure evolutions induced by HCEPB treatment and their effect on the surface property and service performance of M2High Speed Steel.It is showed that when treated by HCPEB, the carbide in the surface layer could be erupted and dissolved, and leave the typical crater forms on the modified surface, associated with carbon content decreased in the comer of the crater and a series of defects, such as microcrack, twin crystal, and so on. Under the same accelerating voltage, along with the numbers of pulse increase, the numbers of crater decreased and the surface trended to be smoother. Under the same numbers of pulse, the higher the accelerating voltage was, the smoother the surface was.The surface of M2HSS was quickly heated and cooled during the process of HCPEB irradation. Distribution, grain size and shape of carbides became smaller and more homogeneous because of its fast melting-solidification. According to the XRD results, along with the numbers of pulse increase, content of carbide and martensite decreased, yet that of austenite increased, with the appearance of stress.Because of the surface morphology and microstructure evolution after HCPEB treatment, the surface properties exhibit the following evolution. The microhardness values measured on the treated surface are all higher than initial sample. The HSS treatd by HCPEB with the voltage of15kV, and25pulses, has the highest hardness, increased by50.6%. Perpendicular to the surface, the microhardness increased in the range of tens of microns, and there is remelting coating with the sickness of6to10μm. The friction coefficients of the M2HSS irradiated by HCPEB were all lower than that of the original samples, and with the pulse numbers increased the friction coefficients increased and then decreased. The wearability is best with the voltage of15kV, and25pulses.