Study Of Low Stress Repeated Impact Deformation Of Laser Cladding Graded Coating

In the engineering field, many important components bear low stress repeatedimpact load.The researches show that the failures of the components which work underrepeated impact load can be attributed to plastic deformation. Previous deformation lawof laser cladding simple substance coating showed ‘skin effect’, which meansdeformation decreases with the increase of collision number, and deformation degreepresents attenuation trend from coating to substrate. Against the phenomenon, gradedcoating which is made by laser cladding is adopted to weaken the influence in thisarticle, the deformation law is analysed after the graded coating is impacted under lowstress, and the strain rate mathematical model of the graded coating and substrate areconstructed in certain assumptions.Uniform distribution graded coating and exponential distribution graded coatingare prepared by laser cladding, with gradient change of Ni content in every layer. Theprepared Ni content of every layer coating is identical with design value,which is foundby XRD. The hardness of the graded coating reduces from surface to centre gradually,which meets the expectation.Meshed the parts and put forward the new way of layered plastic distortionresponse. Repeated impact tests are conducted both of the parts with uniformdistribution graded coating and exponential distribution graded coating under the samecondition (impact stress σ=100Mpa, impact stroke h=22mm, impact frequencyp=2Hz). The test data ia collected according to the established experimental steps, thenprocessed and analysed. Skin effect is found in the graded coating deformation afterrepeated impact. But the deformation is smaller than the laser cladding simple substancecoating.The graded coating has obvious effect in resisting the repeated impact.The hardness of uniform distribution graded coating before and after repeatedimpact test has obvious deformation hardening phenomenon. Hardness difference in the surface is biggest,and the hardening depth is identical with the deformation depth.deformation hardening phenomenon of exponential distribution graded coating occursin the first coating layer and a distance of2mm under the substrate surface.According to the analysis, it is found that the depth is proportional to the exponentof the deformation rate, when the impact number is definite; the strain rate and impacttimes are into a power function relationwhen the depth is definite. Under some assumedcondition, the strain rate models of the coating and the substrate are modeled primarily,regressive analysed and tested with Excel. At last, equation of linear regression andnonlinear regression equation of the coating and the substrate are obtained.