Laser-clad FeCrAl/TiC composite coating on ferrite/martensitic steel: Significant grain refinement and wear resistance enhancement induced by adding TiC

Abstract

By employing laser cladding, the surface of a ferritic/martensite (F/M) steel was coated with FeCrAl metallic and FeCrAl/TiC composite coatings with their microstructures and wear resistance subjected to dedicated characterizations. The thickness of the FeCrAl coating is ~90 μm with its microstructure mainly consisting of coarse columnar grains. In contrast, the FeCrAl/TiC coating is primarily comprised of fine equiaxed grains with a thickness of ~140 μm. It is demonstrated that the addition of TiC could lead to very effective grain refinement, promote their morphology to transform from columnar to equiaxed, and suppress cracks in the coating. Both the laser-clad specimens have a heat-affected zone with 35–40 μm in thickness and mainly comprised of martensitic laths. During the martensitic transformation, the obedience of specific orientation relations (Nishiyama-Wassermann and Kurdjumov-Sachs) produces scattered orientations and featured misorientation characteristics. Wear tests show that both the coatings have greatly reduced wear rates compared with the substrate, and characterizations of their worn tracks suggest all of them to essentially have abrasive and oxidative wear mechanisms. Compared with the FeCrAl metallic coating, the wear resistance of the FeCrAl/TiC composite coating is further considerably improved due largely to the TiC-induced grain refinement.