Nanocrystalline Cermet Coatings for Erosion–Corrosion Protection

• Main Authors: Abhishek Tiwari, Saravanan Seman, Gaurav Singh, Rengaswamy Jayaganthan
• Format: Article
• Language: English
• Published: MDPI AG 2019-06-01
• Series: Coatings
• Subjects: thermal spray; Cr₃C₂-NiCr; erosion–corrosion; wear; nanocrystalline
• Online Access: https://www.mdpi.com/2079-6412/9/6/400

The processing techniques, microstructural characteristics, and erosion corrosion behaviour of Cr₃C₂−NiCr and tungsten carbide (WC)-based cermet coatings are reviewed in this work. Conventional and nanocrystalline Cr₃C₂−NiCr and WC-based cermet coatings are generally synthesized using thermal spray technique. The wear, erosion, and corrosion protection ability of conventional and nanocermet coatings are compared based on available literature. In Cr₃C₂−NiCr coatings, the corrosion resistance is offered by NiCr metal matrix while the wear resistance is provided by the carbide ceramic phase, making it suitable for erosion−corrosion protection. The nanocrystalline cermet coatings exhibits better erosion−corrosion resistance as compared to the conventional coatings. The nanocrystalline coatings reduces the erosion−corrosion rate significantly compared to conventional coatings. It is attributed to the presence of the protective NiCr metallic binder that allows easier and faster re-passivation when the coating is subjected to wear and the fine-grain structure with homogeneous distribution of the skeleton network of hard carbide phases. In addition, corrosion-accelerated erosion dominates the reaction mechanism of erosion−corrosion and, therefore, higher hardness, strength, and better wear resistance of nanocermet coating along with its faster repassivation kinetics accounts for improved corrosion resistance as compared to conventional coatings.