Research On Preparation And Performance Of Inconel 718 Coating By Laser Cladding

To satisfy the requirements for the repair and performance enhancement of key aero-engine components.Laser cladding was used to create an Inconel 718 coating on an A286 substrate.In this study,orthogonal experiments were designed first.The laser cladding process was studied and optimized using gray multi-objective optimization based on coating performance.Furthermore,the parameters that have a significant influence on the performance of different laser-clad coatings are obtained using ANOVA(analysis of variance)and SNR(signal to noise ratio)analysis,and the variation rule of the performance of laser-clad coatings with parameters is given.The microstructure of the coating test samples was analyzed,and it was discovered that the In718 coating prepared with the chosen laser cladding parameters exhibited Nb element segregation.When the degree of Nb element segregation was too high,significant Laves phases were generated between grains,and the increase in Laves phase content was the primary cause of the laser cladding coating’s decrease in microhardness.The shear fracture roughness of In718 coatings prepared using the selected laser cladding parameters varies,which may be related to the uniformity of the microstructure of the bonding interface between the coating substrate and the laser cladding parameters.In the tensile test,the main fracture mechanism of the In718 coating sample prepared by the selected laser cladding parameters is plastic fracture.The fracture mechanism of a small amount of coating samples is a mixed brittle-plastic fracture mechanism.By analyzing the friction and wear properties of the laser cladding coating after multi-objective optimization and the microstructure of relevant test samples,it was found that there is still intergranular Nb element segregation in the optimized laser cladding coating.After optimization,the shear fracture surface of the laser cladding coating is relatively flat,but the microstructure in the optimized laser cladding coating is still uneven.After optimization,the fracture mode of the laser cladding coating is a mixed brittle-plastic fracture mechanism.During the friction and wear tests of the optimized laser cladding coating at different temperatures,as the test temperature increases,the degree of oxidation and wear of the optimized laser cladding coating increases,while the degree of adhesive wear decreases.This study further conducted multi-level heat treatment on the laser cladding coating after multi-objective optimization.The performance of laser cladding coatings after heat treatment was tested,and the microstructure and elemental composition of relevant test samples were analyzed.It was found that after heat treatment,the internal thickness of the laser cladding coating decreased due to the degree of Nb element segregation and needle-like structure.The generation of phases has significantly increased the microhardness of laser cladding coatings.After heat treatment,the fracture surface of the shear layer of the laser cladding coating is generally smoother,and the structure is more uniform.The bonding performance between the coating and the substrate is further improved.After heat treatment,the yield strength and ultimate tensile strength of the laser cladding coating have significantly increased,but there is a certain decrease in elongation.The fracture mode of laser cladding coatings remains a mixed brittle-plastic fracture mechanism.During the friction and wear tests of the optimized laser cladding coating at different temperatures,as the test temperature increases,the laser cladding coating after heat treatment also exhibits an increase in oxidation wear and a decrease in adhesive wear.There are 52 figures,32 tables,and 90 reference in this thesis.