Study On Texture Pattern Fabrication And Fatigue Properties Of Ni60 Coating

With the rapid development of China's machinery manufacturing industry,bearing parts play an important role in the service process.However,during the operation of the bearing parts,it is easy to be subjected to cyclic stress to generate fatigue cracks and form fatigue wear,and the resulting failure brings serious economic losses.Therefore,these important mechanical parts are required to extend their service life.The use of advanced surface engineering techniques to change the surface characteristics of parts to improve fatigue wear resistance is one of the current effective methods,and can control economic costs and reduce environmental pollution.In this thesis,we combine plasma thermal spraying technology and laser surface texturing technology to spraying Ni60 coating on 45 steel substrate and processing different texture patterns.Comprehensively analyzed the influence of coating on bearing surface properties.And studied the influence of different textures' parameters on oil wettability and contact fatigue performance,which could further improve the rolling contact fatigue performance of the workpiece.The morphology of the laser processing parameters on the surface of Ni60 coating was studied.The surface morphology was evaluated by SEM,and the depth of the texture pattern was observed by 3D scanner.It was f-ound that changing the laser power and scanning speed can obtain pit depths of different diameters,and changing the number of processing can obtain stripe depths of different widths.The Ni60 coating surface is processed by laser can significantly improve the hardness of the texture pattern,and the changes of its hardness exhibit a soft and hard alternating phase,which can prevent the crack from expanding.The effect of texture pattern on oil wettability and fatigue life was studied by orthogonal test.It was found that the depth of the texture pattern is the most influential factor for oil wettability and fatigue failure life.As the depth increases,the oil wettability and the contact fatigue life.When the area ratio is small,the pits,stripes,and grid-like texture patterns are processed,which found that the pit-like texture have the best fatigue wear resistance.It has analyzed the surface and cross section of the untextured and the textured sample.There are four mechanisms to affect the contact fatigue life:the surface hardness is improved after laser processing;the texture pattern stores the lubricating oil;the texture pattern contains wear debris;but the texture pattern reduces the actual contact area and increases the contact zone stress.The effects of texture parameters on oil wettability and fatigue life were further studied by a single factor test.It was found that oil wettability and surface hardness jointly affect fatigue life.