Effect of Laser Scanning Speed on Microstructure and Corrosion Resistance of Ni-based Alloy Coatings

Abstract:

Ni-based alloy (24wt% Cr, 13wt% Mo, and balanced Ni) coatings were prepared by laser cladding technique on Q235 steel. The effects of laser scanning speed (100, 200, and 300 mm/s) on microstructure and corrosion resistance of coatings were investigated. The microstructures, phase composition, element dilution rate, microhardness, and corrosion resistance of the coatings were analyzed. Results show that coatings consist of γ-Ni(Cr, Mo, Fe) and Cr0.19Fe0.7Ni0.11 solid solution. The grain size is refined, the element dilution rate is decreased, and the microhardness is enhanced with increasing the laser scanning speed. The coating prepared at scanning speed of 100 mm/s exhibits the lowest corrosion potential after immersion in 3.5wt% NaCl solution for 2 h due to its high element dilution rate. Whereas this coating shows better corrosion resistance than the other two coatings do after immersion in 3.5wt% NaCl solution for 7 d due to the good coating quality and stable passive film.

Key words:laser scanning speed;microstructure;corrosion resistance;Ni-based alloy coating