Thermal Spraying Coating of Internal Combustion Related Engines to Mitigate Against Hostile Environments

Thermal spraying can provide thick coatings (approx. thickness range is 20 micrometers to several mm, depending on the process and feed-stock), over a large area at high deposition rate as compared to other coating processes such as electroplating, physical and chemical vapour deposition. Coating materials available for thermal spraying include metals, alloys, ceramics, plastics and composites. They are fed in powder or wire form, heated to a molten or semi-molten state and accelerated towards substrates in the form of micrometer-size particles. Combustion or electrical arc discharge is usually used as the source of energy for thermal spraying. Resulting coatings are made by the accumulation of numerous sprayed particles. The surface may not heat up significantly, allowing the coating of flammable substances.

Since the mid-1960s, the automotive industry has progressed in Europe, Japan, and the United States, and the car market has expanded. The spread in newly emerging countries has increased notably in recent years, and the global volume of automobile sales totalled approximately 72 million in 2011. It is estimated that expansion of the market will continue, due to the increase in income in newly emerging countries.

Coating quality is usually assessed by measuring its porosity, oxide content, macro and micro-hardness, bond strength and surface roughness. Generally, the coating quality increases with increasing particle velocities. These coating provide a barrier for the equipment they are applied onto, to protect their surface from extreme conditions such as wear, corrosion, thermal effects etc.

Auto manufacturers continue to produce cars with improved fuel efficiency (thermal sprayed cylinder bores, heat management of intake and exhaust system parts, combustion chamber walls etc.). This research will build upon this by researching a two component coating system that withstands the extreme thermal/wear conditions and characterised in order to improve engine performance.