Abstract：Using extreme high speed laser cladding technology, 316L coating was prepared on 45 steel shaft. The microstructure
of the coating was observed by scanning electron microscope (SEM), elemental and phase analyses were
carried out by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), the microhardness and wear resistance
of the coating were tested. The results show that the extreme high speed laser cladding technology has a
small spot diameter and a high overlap rate, so the flatness of the coating is high. The energy density is high (about 9×
104 W/cm2), and the powder is completely melted, so the coating has a high density. The volume of the melt is small,
the heat and cold conversion speed is fast, the degree of undercooling ΔT is large, so the grain refinement is obvious.
The middle and lower parts of the coating are composed of small dendrites produced by rapid solidification and interdendritic
eutectic phases, the middle and upper parts grains gradually transform to equiaxed grains. At the overlap
boundary and at the cladding layer/substrate interface, there is a large difference in grain size on both sides. The laser
has a certain dilution effect on the substrate. The coating thickness is uneven, but it is well metallurgical bonded with the base material. The phase of the 316L coating is composed of γ -Fe, Cr0.19Fe0.7Ni0.11, Fe63Mo37. Due to fine grain
strengthening and second phase strengthening mechanism, the average hardness of the 316L coating (634.12HV0.5) is
3.07 times that of the 45 steel substrate. The wear resistance is increased by 31.8%, and the main wear mechanism is
abrasive wear.
2023, Vol. 33 
