EFFECT OF Y₂O₃ ON MICROSTRUCTURE AND CRACKING SUSCEPTIBILITY OF Ni45 COATING BY LASER CLADDING WITH SHIELDING AND CARRIER GAS

Abstract

The Ni45 alloy composite coating was generated on 42 CrMoA alloy steel through laser cladding utilizing a 5[Formula: see text]kW CO2 laser, four-axis CNC machines, and the coaxial powder feeding system in this study. The effect of Y2O3 on the microstructure and cracking susceptibility of the composite coatings was investigated under different shielding gas and carrier gas flow rate conditions. The macroscopic morphology and microstructure were analyzed by optical microscopy, scanning electron microscopy, XRD, and microhardness tester. The results showed that the increase of shielding gas flow rate could reduce the cracking susceptibility of the composite coatings, and the optimum additional amount of Y2O3 was 0.4[Formula: see text]wt.%. In addition, the variation of the carrier gas flow rate has an effect on the cracking susceptibility: An increase followed by a decrease in the flow rate leads to a decrease in the cracking susceptibility. In order to obtain the lowest cracking sensitivity and the best microstructure, the optimum conditions were a shielding gas flow rate of 15[Formula: see text]l /min and a carrier gas flow rate of 550[Formula: see text]l/h.