The Gradient Microstructure and High-Temperature Wear Behavior of the CoCrMoSi Coating by Laser Cladding

Abstract

Recently, laser cladding has been widely investigated for the preparation of Co-based coatings for high-temperature applications. However, there is a highly cracking tendency in Co-based alloys due to the reinforcing hard phases. In this work, a single layer of CoCrMoSi coating was prepared with laser cladding on 304 stainless steel. By proper preheating, cracking was avoided during deposition. The high-temperature wear behaviors of the coating were evaluated by ball-on-disk test. In terms of morphology and chemical composition, the coating exhibited a gradient microstructure across the section. From the interface with the substrate to the top surface, the structure was characterized with three types of morphology in sequence, i.e., coarse cellular crystals in the interdiffusion zone, nanosized lamellar eutectic and Laves-phase dendrites embedded within nanosized lamellar eutectic. The surface hardness of the coating is 835HV0.3, which was mainly attributed to the Laves phase. Compared with the 304 stainless steel, the volume loss of the coating decreased by 76.5%at 400°C. The wear mechanisms of the coating were oxidation wear and abrasive wear. The excellent coating wear resistance at high-temperature can be traced to the microstructure of Laves phase embedded within the nanosized eutectic.