Effect of induction remelting on the microstructure and properties of in situ TiN-reinforced NiCrBSi composite coatings

In this study, NiCrBSi-TiN composite coatings were obtained by plasma spraying NiCrBSi and Ti powders followed by subsequent induction remelting. The microstructural evolution was investigated by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The wear resistance and erosion resistance of as-sprayed NiCrBSi-TiN (ASN) and induction remelted NiCrBSi-TiN (RMN) composite coatings were tested using a block-on-ring tribo-tester and solid-particle erosion configuration, respectively. Key findings suggest that induction remelting changed the microstructure of NiCrBSi-TiN composite coatings, by eliminating defects such as pores and micro-cracks and improved inter-lamellar bonding. A transition layer with a thickness of about 12 μm was formed between the remelted coating and metal substrate which were connected with metallurgical bonds. RMN coatings exhibited better erosion and wear resistance and had a more stable friction behavior compared to ASN coatings.