A PTWA-applied cylinder coating. Click to enlarge.

While an aluminum engine block offers a substantial weight savings to a vehicle, most aluminum engines require heavy cast iron liners because of aluminum’s low wear resistance, somewhat offsetting the block’s initial leaner weight.

The PTWA process, developed by Ford in collaboration with Flame-Spray Industries, replaces these heavy liners with a low-friction, wear-resistant coating that makes the engine lighter and more efficient. The plasma-sprayed coating offers several advantages, including:

• Engine weight reductions—the coating can reduce the weight of a V-6 engine, for instance, by approximately six pounds.
• Reduced friction between the piston rings and cylinder bore, which has been shown to deliver measurable friction reduction.
• Improved oil and fuel economy.
• Improved engine performance due to better heat management.

In addition, the PTWA coating process has been used to recycle damaged and worn aluminum and cast iron engine blocks by applying the wear-resistant coating to the cylinder bore surface. Remanufacturing engines using the PTWA process requires 50% to 80% less energy to produce compared with a new manufactured engine block.

Thermal spray coatings have been used for years in the aerospace industry for increasing the durability and performance of aircraft turbine engines. Ford researchers began collaborating with Flame-Spray Industries and other suppliers in the 1990s to transfer this efficient, lightweight aerospace technology to a low-cost, high-volume application suitable for the auto industry. One of the challenges was to create a robust coating applicator since commonly-used thermal spray devices were not capable of coating cylinder bores of automotive engine blocks.

The innovative PTWA spray torch technology was a significant enabler of making this high-volume coating process more reliable for automotive applications, while offering the economies of scale for low-cost coating of engine cylinder bores.