Microstructure and tribology behaviors of WC coating fabricated by surface mechanical composite strengthening

Abstract

To improve the anti-wear performance of TA1 alloy, composite-strengthening layers were manufactured by applying the surface mechanical composite-strengthening (SMCS) process at room temperature. The micro-structure, micro-mechanical properties, and tribological behaviour of the composite-strengthening layers were studied. The results showed that the composite-strengthening layers consisted of a ∼ 60 μm thick mechanical deformation layer and a ∼ 20 μm thick tungsten carbide rich particle-reinforced coating. The mechanical deformation layer comprised the surface fine-grain zone and subsurface deformation twinning, showing a gradient structure (GS). The surface hardness of the WC coating is 1572 HV, which is ∼ 7.5 times the substrate hardness (210 HV). Sliding wear rates decrease from the raw sample (≈1.624 × 10−3 mm3∙N−1∙m−1) to the composite-strengthening layer (≈4.03 × 10−4 mm3·N−1·m−1). Microstructural characterization of the worn surface showed that the TA1 alloy substrate was subjected to severe adhesive wear, while the SMCS sample showed abrasive wear and oxidative wear. The formation of composite-strengthening layer imparted good mechanical support and stress release for substrate and avoids local stress concentration and the formation mechanism of the composite-strengthening layer in the SMCS process was explained.