Study On Mechanical Properties And Particle Strengthening Mechanism Of Nickel-copper Alloys Deposited By Laser Melting

Nickel Copper(NiCu)alloy has been widely used in ship's pipeline joints,valves,thrusters,heat exchangers,oil pipelines and other fields due to its excellent mechanical properties and corrosion resistance.In this paper,NiCu alloy multilayer samples and NiCu/WC-12Co composite coatings were prepared by laser melting deposition technology.The microstructure and microhardness were analyzed,and the tribological,electrochemical corrosion and mechanical properties were investigated.The contents and research results are as follows:(1)The laser melting deposition single-pass cladding experiment was carried out,study the influence of laser power and scanning speed on coating formation,and optimize the process parameters by observing the single-pass coating width and dilution rate.The effects of laser power and scanning speed on the coating formation were studied.The process parameters were optimized by observing the width and dilution ratio of single pass coating.(2)The effects of WC-12Co proportion on the macromorphology,phase,microhardness,wear and tear,electrochemical corrosion properties of NiCu alloy were studied.The results show that the composite coating phase is mainly composed of Ni-Cu,WC,Co_0.52Cu_0.48,etc.with the increase of WC content,the type of phase remains unchanged and the area of WC peak increases.The average microhardness of the 30 wt.%WC composite coating is 380 HV_0.2,which is 21%higher than that of NiCu alloy.With the increase of WC proportion,the coefficient of dynamic friction of the composite coating increases,and the wear rate decreases first and then increases.The 20 wt.%WC composite coating has the best wear resistance,and the wear rate is only 1.06×10^-3mg/m,which is more than 90%less than that of NiCu alloy.In 3.5wt.%Na Cl solution,30 wt.%WC composite coating has the best corrosion resistance.(3)The multi-layer specimens of NiCu alloy were prepared.The tensile properties of specimens in parallel laser scanning direction and vertical laser scanning direction were tested under two different strain rates.The test results show that the yield strength and tensile strength of each group of samples are higher than the standard.At the same strain rate,the yield strength and tensile strength of the specimens in the vertical direction are slightly higher than those in the parallel direction.In the same direction,the strength of the specimens with the strain rate of10^-4s^-1are slightly higher than those of the specimens with the strain rate of 10^-3s^-1.(4)Based on the quasi-static tensile test,the Johnson-Cook constitutive model is constructed,and the tensile numerical simulation is carried out by the finite element analysis,which is compared with the stress-strain curve of the stretching experiment to verify the accuracy of the model.It provides data and experimental reference for the analysis and prediction of tensile properties of NiCu alloy prepared by laser melting deposition.