Effect of ultrasonic vibration-assisted laser cladding frequency on the microstructure and properties of Fe-0.5C-15Cr alloy cladding layers

In this paper, Fe-0.5C-15Cr wear and corrosion resistant alloy coating was prepared on 3Cr13 stainless steel surface by ultrasonic vibration assisted laser cladding technology. The effects of ultrasonic vibration frequency on the microstructure, microhardness and corrosion resistance of the coating were studied. The results show that the length of the dendrites of the cladding layer decreased significantly after ultrasonic vibration is applied, the grains size is refined significantly, and the morphology of the grain boundary carbides changed from fishbone-like to short rods, when the vibration frequency is 20.2 kHz, the grain refinement is the most significant, and the orientation of the dendrites is obviously weakened. The hardness of the applied ultrasonic vibration specimens increased by 10–20 HV0.2 relative to the non-ultrasonic specimens, with the increase of vibration frequency, the hardness of the cladding layer firstly increased and then slightly decreased, and the peak appeared at 20.2 kHz. The coefficient of friction of the specimens when the ultrasonic frequency of 20.2 kHz is applied is lower than that of the specimens with non-ultrasonic frequency by 12.8 %, and the abrasive wear rate is reduced by 14.3 %. After ultrasonic vibration, the pitting potential of the cladding layer increases, the dimensional passivation current density decreased, the width of the passivation zone becomes wider, and the intergranular corrosion reactivation rate decreased, When the ultrasonic frequency is 20.2 kHz and 20.4 kHz, the pitting corrosion resistance and intergranular corrosion resistance of the cladding layer are significantly improved. This is because the cavitation effect, resonance effect and acoustic flow effect of ultrasonic vibration promote the non-uniform nucleation, refine the dendrites and intergranular carbides, and promote the redistribution of the corrosion-resistant element Cr in the in-grain martensite and grain boundary carbides, increasing the content of Cr in the matrix, and thus improving the wear resistance and corrosion resistance of the cladding layer.