Optimized surface roughening by pulsed water jet for stronger thermal barrier coating

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Cast-iron has been widely used to manufacture automotive engines. When car engines fail, they are typically replaced because**traditional engine remanufacturing techniques are quite expensive. A new remanufacturing technique has been adopted by major**automakers, known as Plasma Transferred Wire Arc (PTWA) coating technology, aims to give a new life to old engines that would**otherwise be scrapped. A coating is applied through PTWA process to the inner-wall of a worn-out engine block that helps restore**it to its original condition. This innovative remanufacturing process requires very little raw materials as well as saves more than**50% CO2 emission associated with the production of a new engine.**Generally, during cast-iron engine remanufacturing process, an expensive nickel-aluminum (Ni-Al) chemical coating is formed**prior to final PTWA coating of carbon steel to increase the overall bond strength. This expensive Ni-Al pre-coating step can be**avoided by using an optimized surface roughness of the substrate and has been reported extensively for aluminum based**engines. Cast-iron is brittle compared to aluminum alloys and difficult to create a significant surface roughness by conventional**roughening processes.**The idea behind this project is to significantly roughen the cast-iron substrate by an inexpensive and environment friendly highpressure**pulsed water jet technology that is expected to create bond strength as high as Ni-Al coating. An optimized surface**roughness on the substrate will not only provide a metallic diffusion bonding during the PTWA coating but also will create**mechanical interlocks between coating and the substrate, increasing the overall bond strength.