Direct laser deposition of yttria-stabilised zirconia (YSZ) coating on 316L stainless steel

This study explores the direct laser energy deposition of yttria-stabilised zirconia (YSZ) coating onto a 316L stainless steel substrate. A coherent and defect-free interface was achieved, with a sound metallurgical bonding formed through the mass transfer between molten YSZ and partially melted stainless steel. A eutectic structure comprising (Fe, Ni) 2 Zr and α-Fe phases was identified at the interface, extending into the base metal along α-Fe grain boundaries, forming a unique tree root pattern. The YSZ coating, consisted of cubic and tetragonal ZrO 2 , exhibited a respective 3.8- and 13-fold increase in hardness and yield strength compared to stainless steel. The coating was approximately 21% less stiff than stainless steel, with a gradual decrease in elastic modulus from the substrate to YSZ coating, mitigating the modulus mismatch.