Details on Ford Use of PTWA with Video

There's a good article on Flame-Spray Industries' PTWA process as it is being used in the Ford Mustang Shelby GT500 and Nissan GT-R. This article delves a little deeper into the technical apsects than some of the other recent news coverage:

The process in question is called plasma-transferred wire arc (PTWA). It basically involves blowing a fine mist of molten steel at high speed onto a rough surface and then honing that surface into a perfect cylinder bore. It's something that Matthew Zaluzec, Ford's manager of materials and nanotechnology, has been working on since 1991. As the concept was being refined, Ford brought in partners Flamespray and Honsel to finish the development work. The two firms were also responsible for manufacturing and marketing the twenty-five patents that resulted from the research.

The amazing part about this process is its relative simplicity: Spray-on surface processes have been used in aerospace applications for two decades, but until recently, the costs that work in that environment haven't been compatible with mass-market products. It starts with the engine block — aluminum in this case — where the surface to be coated is roughed up in order to give the liner material something to adhere to. Next, specially designed equipment uses an argon-hydrogen plasma arc to atomize an advancing 1010 steel alloy 1/16th-inch wire (basically welding wire). The atomized wire is then sprayed against the cylinder wall at 358 mph. The head lays down layer after layer of this material. Because the particles are so small, they splatter and transfer heat rapidly. They leave behind layers of iron and a ferrous oxide called Weustite (no, it's not rust); these layers build up to a thickness of roughly 0.6 mm, and the block is then honed to a cross-hatch pattern and given a final liner thickness of roughly 150 microns.

 This article also provides a great video of the process...

 
Hot Rodder Tradition Goes Mainstream

Caroll Shelby, founder of Shelby American, is quoted in a CNBC article regarding Ford's decision to use PTWA in the 2011 Ford Mustang Shelby GT500:

"Cutting weight to improve performance is a tradition among hot rodders," said Carroll Shelby, founder of Shelby American. "It might not be as sexy as adding more horsepower or bigger brakes, but shaving pounds off of a car is the single smartest move you can make." The new engine uses state-of-the-art Plasma Transferred Wire Arc (PTWA) liner coating, a process that applies a 150-micron composite coating that contains nanoparticles on the internal surfaces of engine cylinder bores, replacing cast-iron liners typically used in aluminum engine blocks. The Intellectual Property Owners Education Foundation honored the inventors of the Ford-patented PTWA technology with the 2009 National Inventor of the Year Award.

 
Pioneering Process Observes Motor Trend

Sometimes it's the incremental changes made by the adoption of new technology that can make the greatest difference in performance. Motor Trends magazine takes a look at how the Ford Mustang Shelby GT500 makes use of new technology:

Instead, Ford's Special Vehicles Team decided that the Lotus philosophy of "add lightness" was the way to go. The 5.4's heavy iron block was shuffled off to the scrap heap, replaced by an all-aluminum version of itself. That little trick alone was good for 102 lbs in weight savings.

Of course, aluminum isn't as resistant to the explosions commonly found inside the internal combustion engine as iron and steel, so aluminum-block engines typically require heavy steel liners for the cylinders. To avoid the extra 8.5 lbs of weight gain steel liners would have added, Ford pioneered a process known as Plasma Transferred Wire Arc coating in which a jet of 35,000-degree plasma melts a steel wire and blows the molten steel against the cylinder walls. As it cools, the steel oxidizes to form a super-strong, iron-iron oxide coating.
 
Car and Driver Points Out Weight Savings

Car and Driver magazine couldn't help but note that weight savings is only one of the benefits that the 2011 Ford Mustang Shelby GT500 gained be utilizing Flame-Spray Industries' PTWA process:

The aluminum-based supercharged 5.4-liter engine saves 102 pounds compared to the outgoing one. A process called Plasma-Transferred Wire Arc (PTWA) is being used to line the cylinders; a steel wire is melted and sprayed onto the cylinder walls, which are then machined. Along with the obvious weight savings over the cast-iron liners from the Ford GT’s version of the engine, the process is also said to improve heat transfer and reduce friction. The engine sports blue valve covers and a bright-silver supercharger similar to those of the GT.

 
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