Strengthening and toughening mechanism of laser cladding Fe-based coating on plunger surface

Iron-based coating with high hardness are prepared on the plunger surface by laser cladding technology,and the structure characteristic and wear resistance are studied by means of SEM,XRD,EPMA and TEM,and then the strengthening and toughening mechanism is presented. The results show that the laser clad Fe-based coating has good forming without cracks and pores,as well as metallurgical bonding with the matrix, which composed of (Ni,Fe) solid solution,(Cr,Fe)₂₃C₆ carbides and a little twin martensite. The strengthening and toughening mechanism is grains refinement, solid solution strengthening,dispersion strengthening and martensite strengthening. The combined effects of (Ni,Fe) solid solution and refined grains ensure the toughness of Fe-based coating. The microhardness of the coating is 4 times higher than the one of 45 steel,with the maximum value of 850HV_0.2. The resistance of laser clad coating is also higher than the one of 45 steel,and the worn surface of 45# steel is fatigue flake,which of clad coating is smooth,and the scratch is shallow,and the wear mechanism is abrasive wear.