Microstructure and corrosion-wear behaviors for laser cladding repaired martensitic stainless steels using Co-based and Ni-based powders

Abstract

Structural components always suffer severe surface damage (i.e., abrasion and erosion) during long-term service in harsh environments, and laser cladding is a highly efficient method for repairing components. In this work, the laser cladding technique was conducted on 1Cr12 martensitic stainless steel using Co-based and Ni-based alloys as feedstocks for improved wear/corrosion resistance, and the defect density, microstructural evolution, and corrosion-wear resistances of the repaired counterparts were systematically evaluated. Results show that the defect densities of CoCrMo+WC and NiCoCr repaired parts are comparatively high at 1.61 % and 0.98 %, respectively. In contrast, NiCrMoNb+WC and Stellite 6 repaired parts exhibit more favorable dilution rates, reaching 5.4 % and 3.1 %, respectively. The coatings evolve from columnar dendrites to equiaxed grains along the building direction. Moreover, the addition of WC particles significantly hinders the epitaxial growth of columnar dendrites, leading to local orientation variations and a transition from columnar to equiaxed crystals with refined grains. The corrosion resistance and tribological properties of the 1Cr12 matrix are significantly improved after reparation, and Stellite 6 repaired parts exhibit a high pitting potential of about 0.83 VSCE in a chloride-containing solution, together with a low wear rate of 1.4 × 10−5 mm3/N m. The underlying wear resistance mechanisms for different laser cladding candidates are elucidated and our work demonstrates that the Co-based and Ni-based alloys are excellent coating materials for repairing structural components.