Thermal Spraying of Cylinder Bores With the PTWA Internal Coating System

A major goal for the automotive industry over the next years is the reduction in CO₂ emissions. This can be accomplished by reducing fuel consumption for new production vehicles and by increased remanufacturing of old worn engines. Both of these objectives can be addressed with the use of PTWA (Plasma Transferred Wire Arc) thermal spray of cylinder bores. Key factors in this development relating to new production engines focus on the reduction in overall vehicle weight and also the improvement of engine efficiency by reducing the internal friction losses. Substantial weight savings can be achieved with the use of aluminum engines. However, most aluminum engines require cast iron liners to be used as the wear surface. Additional weight savings and potential friction reduction can be achieved by replacing these heavy cast iron liners with a low friction, wear resistant PTWA coatings on the cylinder bores. In addition to being applied to new engines for automotive production, this same process can also be used to repair worn cylinder bores in both aluminum and cast iron engine blocks. This technology makes it possible to salvage engine blocks that would otherwise be scrapped. In addition, PTWA thermal spray can be used to reduce costs for engines that are already remanufactured using expensive over-sized pistons. With reduced costs and salvaging previously scrapped components, the use of the thermal spray technology can increase the amount of remanufacturing for critical engine components. The reduced CO₂ emissions results from remanufactured components requiring 50% to 80% less energy to produce than the new production manufactured equivalents [1].