Synthesis of fused mullite and its use in multifunctional nickel based composite coating

Fused mullite, a commonly used refractory material has been synthesized and adopted in the present study as reinforcement in the nickel composite coating. The composite has been developed through electrodeposition method. The thermal stability of Ni–mullite composite in terms of microhardness was studied at temperatures up to 800 °C and compared with Ni–SiC, a commercialized wear resistant coating. The microhardness of as deposited electroforms was similar for both Ni–mullite and Ni–SiC composites (400 Hk). A marginal decrease in the microhardness of Ni–mullite occurred at 600 °C while, significant reduction was observed beyond 400 °C for Ni–SiC coating. Thus, the Ni–mullite composite has higher thermal stability compared to Ni–SiC. The tribological studies showed that the wear volume loss for Ni–mullite is 2.38 × 10− 5 mm3/m while, of Ni–SiC it is 9.58 × 10− 5 mm3/m under identical conditions. The potentiodynamic polarization and electrochemical impedance showed that the corrosion resistance of Ni–mullite composite is better compared to Ni–SiC. Thus, Ni–mullite is a multifunctional coating.