Investigation On Abrasion And Wear Properties Of Ni-Cu-Si Coating Prepared By Laser Cladding On Tool Steel

The H13 steel is a kind of tool steels which is widely used in many fields.H13 steel works on bad conditions which include high temperature wear and the periodic change of temperature.During such conditions,it is very common for H13 steel tools to be worn,corroded and oxided,which in turn leads to fail.Hence,it is essential to improve the wear and corrosion resistance,the high temperature oxidation resistance to prolong its lifetime.In this thesis,Ni-Cu-Si coatings were fabricated via laser cladding technology.The surface morphology,microstructure of the coating,phase constituents,wear resistance,high temperature oxidation resistance and corrosion resistance in 3.5%NaCl solution were investigated using Laser Scanning Confocal Microscopy(LSCM),Optical Microscopy(OM),X-ray diffraction(XRD),Scaning Electron Microscopy(SEM)equipped with Energy Disperse Spectroscopy(EDS).The results are as following.Ni-Cu and Ni-Cu-Si coatings with sound morphologies and metallurgical bonding with H13 substrate were prepared with such parameters as pulse width of 2.4 ms,pulse frequency of 30 Hz,defocus distance of-6.9 mm,current of 100 A,scanning speed of 120 mm/min.SiO2 addition has a significant influence on refining microstructure of Ni-Cu coating.XRD results show that phase constituents changed with addition of SiO2,the supersaturated solid solution of ?(Fe-Ni)phase was detected in all samples.The results of wear experimental indicate that the friction coefficient of Ni-Cu + 30 wt.%SiO2 coating is smaller than H13 steel substrate,while that of Ni-Cu,Ni-Cu + 10 wt.%SiO2 and Ni-Cu + 20 wt.%SiO2 coatings is larger than H13 substrate.The weight loss increased with increasing of applied load.The weight loss of Ni-Cu-Si coatings with different SiO2 content is less than that of H13 steel and present decreasing trend with increasing of SiO2 content.The wear mechanism of H13 steel,Ni-Cu coating,and Ni-Cu-Si coating can be characterized as adhesive wear,both adhesive wear and abrasive wear,and abrasive wear,respectively.Ni-Cu + 30 wt.%SiO2 coating shows the best wear resistance within the scope of the research.The results of electrochemical corrosion reveal that the corrosion potential and corrosion current intensity of Ni-Cu and Ni-Cu-Si coatings are lower than that of H13 steel substrate,indicating that tendency of corrosion resistance of H13 steel was reduced and the corrosion resistance was improved by laser cladding Ni-Cu and Ni-Cu-Si coatings.SiO2 content has a significant influence on corrosion resistance;a higher content is not beneficial for improving corrosion resistance.The coating with 10 wt.%SiO2 addition presents best corrosion resistance.The results of high temperature oxidation experiments show that the high temperature oxidation resistance of H13 steel was improved by laser cladding Ni-Cu and Ni-Cu-Si coatings.Compared to Ni-Cu coating,Ni-Cu-Si coatings presents more excellent high temperature oxidation resistance,meanwhile,higher content of SiO2 presents better high temperature oxidation resistance.