Dendrite refinement and wear performance enhancement in laser-cladded Fe-based coatings after multi-step laser remelting

Abstract

In this work, Fe-based coatings were prepared by laser cladding and the effects of multi-step laser remelting (MLR) on phase components, microstructure evolution, hardness and wear behavior were investigated. The as-cladded coating exhibits a complex phase structure and no obvious variation is observed when remelted for 1–3 times. The as-cladded coating comprises three structures including Mo-rich dendrites, γ-(Fe, Cr) matrix and several kinds of intermetallic compounds. The Mo-rich dendrites were gradually refined to nanoscale size grains with the increase of remelting times. The Vickers hardness and wear resistance of the Fe-based coatings improves firstly and then aggravates with the MLR process. The highest hardness of 1487.4 HV0.1 and the smallest wear rate of (0.21 ± 0.01) × 10−6 mm3/(N·m) is obtained when the coating is remelted twice. The improved wear performance mainly comes from the existence of hard intermetallic compounds and the refinement of Mo-rich dendrites. Despite a slight compensation of hardness and wear resistance, the coating remelted for three times also exhibits an excellent wear performance due to the microstructure homogenization and the absence of fatigue damage. This work broadens the opportunities to the microstructure modification and property optimization for laser-cladded coatings and presents further understanding on laser manufacturing technology.