Steel Roll Of Plasma Spraying Strengthen Processing Technology And Study Of Structure And Properties

Ni60B coating and Cr₃C₂-NiCr coating were prepared through the plasma sprayingtechnology on steel roll substrate surface in this paper. Optimized the spraying processparameters, used tensile test, hardness test and thermal shock test with other relatedequipments or instruments, and had a research of coating structure and property.As the index of the combination strength of coating and substrate, by the orthogonalexperiment method, optimized the main parameters of spraying--namely spraying distance,the main steam flow, the sending powder amount and spraying power, and analyzed theevery parameter influence law on the coating structure and properties. Observed the fracturetensile test, fracture mainly happened in coating and substrate. The coating under theoptimization parameters, its bonding strength was greater than the group beforeoptimization samples strength. Ni60B coating binding strength after optimization was59.311MPa, Cr₃C₂-NiCr coating binding strength after optimization was68.491MPa,realized the optimization effect.Prepared the metallographic specimen of coating, to observe the microstructureobservation, the coatings are characteristic of lamellar microstructure and porosities, microcracks. The coalescent between coating and substrate is most of mechanical bond. Theoptimized coating organization, the number of pore, crack defects reduced significantly.XRD analysis showed that the before and after spraying, coating material did not appearobvious phase change, had kept the original powder characteristics，such as high hardnessetc. Coating’s micro hardness of parallel to the matrix and perpendicular to the direction ofthe matrix, coating micro hardness was dispersion, but accorded with normal distributionsignificantly.The thermal shock test of Ni60B coating and Cr₃C₂-NiCr coating, it found that twocoating both had a good thermal shock performance, a high fever fatigue life. The thermalshock temperature were selected as650℃and450℃, after the thermal shock test, foundthat the higher thermal shock temperature, the thermal fatigue life was short; Conversely,life was long. The main failure forms of the coating were the cracks of the coating initiate,expanded and then overall peel from the interface along the coating and substrate, and thefailure of small pieces off. The thermal temperature had a larger influence of thermal shock failure forms.