Effect of laser remelting power on the microstructure and properties of vanadizing layer on AISI 52100 steel pin shaft.

The surface of AISI 52100 steel was pre-treated by laser remelting with different powers, and the vanadizing layer were prepared on remelted steel by pack cementation. The microstructure and properties of vanadizing layer were investigated by XRD, microhardness tester, metallographic microscope, scanning electron microscope, energy dispersive spectrometer, friction and wear tester. The critical load L was determined by observing the micro-scratch morphology of scratches through micro-scratch experiments, and its wear performance was studied. The results show that the hardness of remelting zone increase with the increase of laser power. When the laser power is 500 W, the microhardness is 424.6 HV. The vanadizing layer formed on the remelting surfaces is uniform and dense. The layers are mainly composed of VC phase and α-Fe/α'-Fe phase, the VC phase has the preferred orientation of (200) and (111) planes. There is a good metallurgical bonding between the vanadizing layer and the steel， and the thickness is 2.7 μm-12.15 μm, the microhardness is 2050.7 HV-2350.9 HV. When the laser remelting power is 300 W, the vanadizing layer is better in thickness, microhardness and average friction coefficient, the bonding force Lc between the vanadizing layer and the substrate is about 41.59 N, and the main failure mode is the spalling of the vanadizing layer. It can be concluded that laser remelting pre-treatment can greatly improve the hardness and wear resistance.