Tribological properties and wear mechanism of Ni@Gr reinforced Ni-based alloy coatings prepared via laser cladding

Laser cladding is an advanced surface engineering technology capable of producing Ni-based coatings with high wear resistance. Incorporating graphene (Gr) into Ni-based coatings has great potential for improving the tribological properties of component surface. To date, the effects of Ni-decorated Gr (Ni@Gr) content on the tribological properties of Ni@Gr/Ni-based composite coatings and their surface wear mechanism have yet to be fully understood. In this study, Ni@Gr/Ni-based composite coatings with varying Ni@Gr contents (0, 2, 4, and 6 wt%) were prepared by laser cladding, and the effects of different Ni@Gr contents on the microstructure and tribological properties were investigated in detail. The results showed that the incorporation of Ni@Gr resulted in significant grain refinement and enhanced dislocations, along with an increase in carbide content. The smallest grain size (2.88 μm) and highest hardness (1039.3 HV0.2) were observed in the Ni@Gr/Ni-based composite coating with 4 wt% Ni@Gr. Simultaneously, the coefficient of the friction (COF) and the wear volume of the coating reach the minimum values of 0.3221 and 2.0123 × 10−2 mm−3, representing a 15.44% and 36.29% reduction compared to the pure Ni-based alloy coating, respectively. Based on the observed results, the wear mechanism of Ni@Gr/Ni-based composite coatings was analyzed and revealed. The high wear resistance of the coating is attributed to the optimal mechanical properties resulting from grain refinement and dislocation strengthening, as well as the uniformly distributed Ni@Gr with easily sheared layered structures that generate a lubricating film, effectively reducing the contact area between the coating and the grinding ball while resisting friction loads. This study could provide a deep understanding of the wear mechanism of Gr-doped surface coatings, contributing to the advancement of this field.