Interface characteristics and dry sliding wear behaviour of hardfaced stellite 6 overlays on ASTM A36 structural steel

• Dendritic γ-Co matrix with Cr/W carbides formed a sound, crack-free interface. • Overlay showed epitaxial growth, strong texture, and lower residual strain. • Stellite 6 hardness was ∼1.7 × higher than A36 due to solution and carbide strengthening. • Wear tests showed ∼94% lower mass loss and reduced CoF for the Stellite 6 overlay. • Stellite 6 showed mild oxidative wear, unlike the severe abrasive wear on A36. Cobalt-based Stellite 6 alloy is widely used in turbine blades, valve seats, and power plant components due to its excellent wear and corrosion resistance. In this study, Stellite 6 was hardfaced over ASTM A36 structural steel using the gas metal arc welding (GMAW) process to improve the surface integrity of the weaker substrate. Microstructural analysis revealed that the hard overlay consisted of a γ-Co solid-solution matrix reinforced with Cr- and W-rich carbides distributed along interdendritic regions. Secondary electron micrographs revealed ferrite-pearlite characteristics in the substrate and confirmed the presence of columnar and equiaxed dendrites in the overlay. Electron backscatter diffraction (EBSD) analysis confirmed epitaxial dendritic growth with strong {001}/{100} texture in the overlay and sound metallurgical bonding at the interface. The Stellite 6 layer exhibited an average hardness of 448 ± 13.5 HV and nano-hardness of 6.5-8.5 GPa, nearly 3 times higher than the substrate (2-2.5 GPa), due to solid-solution strengthening and carbide dispersion. Dry sliding wear tests revealed a 94% reduction in mass loss for the overlay (∼75.7 ± 2 mg) compared to the A36 substrate (∼1288 ± 25 mg), accompanied by a lower and more stable coefficient of friction (0.45 ± 0.04). The improved wear resistance is attributed to the dendritic microstructure with carbides in the interdendritic regions and to the formation of a protective tribo-oxide film that minimizes both adhesive and abrasive wear. GMAW-deposited Stellite 6 overlays significantly enhance the hardness and tribological performance of A36 steel, making them highly suitable for wear-critical industrial applications.