Structure Evolution And Mechanical Properties Of Ni60Alloy Laser Cladding Layer

In this paper, Ni60self fluxed alloy powder was used as cladding material,45steel assubstrate material, we discuss the influence of different process parameters on the lasercladding single layer of the macroscopic characteristics, microstructure and mechanicalproperties.With the scan rate gradually increased, the cladding layer width, the depth of moltenpool and the dilution rate would decrease gradually, the cladding layer height and contactangle gradually increased. But when the laser power gradually increased, the width andheight of the cladding layer, the depth of molten pool, the contact angle and the dilutionrate would gradually increased. The contact angle and the dilution rate were an importantcontrol standard of cladding layer forming quality.Microstructure of Ni-base alloys included γ-Ni solid solution, chrome boride CrB,nickel boride Ni3B and Ni2B, carbide M₇C₃and M₂₃C₆composition. The cladding layerinterface place was typical dendrites, the middle of cladding layer was columnar dendritesor a thick dendrites, the top of the cladding layer was the cellular crystal or columnarcrystal, these microscopic structure changes were mainly depended on large temperaturegradient and cooling rate. With the increase of the rate of dilution, between coating layerand substrate elements of the diffusion ability increased, the cladding layer of Fe elementsof the percentage increased gradually, and Ni, Si, Cr element percentage graduallyreduced.Combined with nano-indentation technical analysis from the substrate to claddinglayer top hardness was obvious gradient distribution rule. Compared with the substratehardness of3.1GPa, laser cladding layer hardness value of11-14GPa, was4timesapproximately larger than that of the substrate, far outweighed the substrate hardnessvalue. When scanning speed gradually increased, the gain of the cladding layer hardnessincrease gradually, gradually reduced the friction coefficient. When the laser powerincreased, the hardness decreased gradually, friction coefficient increased instead. Thefriction coefficient depends largely on the cladding layer surface hardness. Hardness distribution of the turning point position variation, macroscopic features in combinationinterface position change and microstructure transformation point position change followthe same trence, which indicate that the cladding layer microcosmic structure determin itsmechanical performance.