Abstract

This thesis focuses on the development and evaluation of Cu-based coatings, specifically CuNiIn and self-lubricating CuNiIn/MoS₂ composites, fabricated using low-temperature thermal spray techniques. High Velocity Oxy-Fuel (HVOF), High Velocity Air-Fuel (HVAF), and Inner Diameter High Velocity Air-Fuel (ID-HVAF) processes were employed to deposit dense, low-porosity coatings aimed at improving tribological performance and reducing oxidation during fabrication.
Comprehensive microstructural and phase characterizations were performed using Field Emission Scanning Electron Microscopy (FE-SEM) to analyze surface and cross-sectional morphologies, X-ray Diffraction (XRD) to identify phase composition, and Raman Spectroscopy to confirm the integrity and distribution of MoS₂ in the composite coatings. Mechanical properties were evaluated through Vickers microhardness testing, and the tribological behavior of the coatings was systematically assessed using high-temperature reciprocating sliding wear tests at room temperature and 450 °C, simulating demanding service conditions.
The results revealed that coatings produced by HVAF and ID-HVAF exhibited significantly lower porosity and oxide content compared to HVOF, leading to improved mechanical integrity and wear resistance. The incorporation of MoS₂ as a solid lubricant within the CuNiIn matrix resulted in a substantial reduction in friction coefficient and wear rate, particularly at elevated temperatures, due to the formation of stable tribofilms and transfer layers at the sliding interface.
This study demonstrates the potential of HVAF-sprayed self-lubricating CuNiIn/MoS₂ composite coatings as high-performance solutions for aerospace and industrial components subjected to fretting and sliding wear. The findings contribute to the advancement of environmentally friendly and energy-efficient surface engineering technologies.