Effects of the Alloy Composition on the Microstructure and Properties of Laser Cladding Ni-based Alloy Coatings

In order to study the relationship between the microstructure and properties of the laser cladding Ni-based alloy coatings,Ni25,Ni45,Ni60 alloy coatings were fabricated on the substrate of 45# steel by laser cladding of the corresponding Ni-based self-fluxing alloy powders at the same process parameters.The microstructure,phase composition and microhardness have been analyzed by the scanning electron microscopy(SEM),X-ray diffractometry(XRD),energy dispersive X-ray spectroscopy(EDS) and microhardness meaurement,respectively.The results show that with increasing alloying element contents,the microstructure of coatings changes from the hypoeutectic to hypereutectic structure,the volume fraction and the size of γ-Ni austenite dendrites and the width of bonding zone between the coating and substrate decrease,but the volume fraction of the interdendritic eutectics and hard phases and the microhardness of the coatings increase from the laser cladding Ni25 to Ni60 alloy coatings.The average microhardness of the laser cladding Ni25,Ni45 alloy coatings are about 250 HV and 550 HV,respectively.However,the average microhardness of the Ni60 alloy coating is about up to 750 HV.It is three times that of the Ni25 alloy coating.