Tribological Properties Laser-Cladded Spherical WB-Reinforced Co-Based Coatings under Low-Temperature Friction

Abstract

Three groups of spherical WB-reinforced Co-based coatings (Co coating, Co + 15%WB coating, Co + 45%WB coating) were fabricated by laser-cladded technology. The microstructure and constituent phase of spherical WB-reinforced Co-based coatings were examined through scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). The low-temperature tribological properties were analyzed by coefficient of friction, 2D and 3D profiles across the wear track, and wear surface morphology, respectively. The results showed that the phases in the WB-reinforced Co-based coatings are mainly γ-Co, carbides Cr23C6 and Cr7C3, WB, and WO3. Under dry sliding friction at −20 °C, the more spherical WB, the lower the friction coefficient. The wear rate of Co + 45%WB coating was as low as 3.567 × 10−4 mm3/N·m−1, indicating the outstanding wear resistance. Abrasive wear was observed on the rough surface of the WB-added coatings. Compared with dry sliding, due to the plastic deformation of micro-convexes and lubrication function in the 3.5 wt.% NaCl solution, the wear tracks on the surfaces of the three tested coatings were shallower, exhibiting distinct elongated plough grooves.

Keywords

• low-temperature friction
• tribological behavior
• Co-based coating
• spherical tungsten boride (WB)