Microstructure and Microhardness of Electroless Nickel-Phosphorous Multiwalled Carbon Nanotube Composite Coatings on Nimonic C263 Superalloy

Nickel-based superalloys are becoming common in the automotive exhaust and turbocharger systems, wherein components are subjected to extreme thermal, mechanical, and oxidative conditions. Nimonic C263 exhibits high-temperature strength and creep resistance. But its surface is susceptible to degradation under service conditions. Electroless composite deposition is a surface engineering technique in which metal ions are chemically reduced and deposited onto the substrate without external electrical energy, enabling uniform and adherent coatings. In this study, electroless nickel-phosphorous (Ni–P)/multiwalled carbon nanotube (MWCNT) composite coating has been deposited on Nimonic C263 substrates. Two carbon nanotube (CNT) concentrations (0.20 g and 0.36 g) were investigated. Scanning electron microscopy (SEM) was used to analyze surface morphology and CNT dispersion, while micro-Vickers hardness testing was conducted in accordance with ASTM E384 using a diamond pyramid indenter at a load of 100 g and a dwell time of 15 s. The Ni–P/0.20 g MWCNT coating exhibited superior hardness due to uniform CNT dispersion and improved microstructural characteristics. Higher CNT concentration results in agglomeration and reduced coating efficiency.

The experimental findings would be a quality dataset to optimize composite coating in future with the use of artificial intelligence and machine learning. The paper emphasizes the uniqueness of coating Nimonic C263 superalloy with Ni–P/MWCNT composite coatings, which is not as extensively studied as traditional materials. The best CNT concentration of 0.20 g is found in order to experience the best microstructural uniformity and hardness. The findings provide a definite structure–property relationship between the dispersion of CNT and mechanical performance, which makes the coating to be practical in high-temperature automotive applications.