Plasma transferred wire arc (PTWA) thermal spraying is a thermal spraying process that deposits a coating on the internal surface of a cylindrical surface, or external surface of any geometry. It is predominantly known for its use in coating the cylinder bores of an

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...

, enabling the construction of

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

engine blocks without

cast iron Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...

cylinder sleeves. The inventors of PTWA received the 2009 IPO National Inventor of the Year award. This technology was initially

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...

ed and developed by

Flame-Spray Industries Flame-Spray Industries, Inc. is a thermal spray company, that invented the plasma transferred wire arc thermal spraying process. They received the 2009 Intellectual Property Owners Association, IPO National Inventor of the Year award for this proc ...

, and subsequently improved upon by Flame-Spray and Ford.

Process

A single conductive wire is used as

feedstock A raw material, also known as a feedstock, unprocessed material, or primary commodity, is a basic material that is used to produce goods, finished goods, energy, or intermediate materials that are feedstock for future finished products. As feedst ...

for the system. A supersonic

plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...

jet—formed by a transferred arc between a non-consumable

cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...

and the wire—melts and atomizes the wire. A stream of air transports the atomized metal onto the substrate. The particles flatten upon striking the surface of the substrate due to their high

kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accele ...

. The particles rapidly solidify upon contact and can assume both crystalline and

amorphous In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid, glassy solid) is a solid that lacks the long-range order that is characteristic of a crystal. Etymology The term comes from the Greek ''a'' ("wi ...

phases. There is also the possibility of producing multi-layer coatings via stacked layers of particles, increasing

wear Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical (e.g., erosion) or chemical (e.g., corrosion). The study of wear and related processes is referred to as tribology. Wear in m ...

resistance. All conductive wires up to and including can be used as feedstock material, including "cored" wires.

Refractory metals Refractory metals are a class of metals that are extraordinarily resistant to heat and wear. The expression is mostly used in the context of materials science, metallurgy and engineering. The definition of which elements belong to this group diff ...

, as well as low melt materials, are easily deposited.

Applications

PTWA can be used to apply a coating to wear surfaces of engine or transmission components, serving as a plain bearing. For the cylinder bores of hypoeutectic aluminum-silicon alloy blocks, PTWA's main advantages over cast iron liners are reduced weight and cost. The thinner bore surface also allows for more compact bore spacing, and can potentially provide better

heat transfer Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...

. Automotive engines that use PTWA include the BMW B58,

Nissan , trade name, trading as Nissan Motor Corporation and often shortened to Nissan, is a Japanese multinational corporation, multinational Automotive industry, automobile manufacturer headquartered in Nishi-ku, Yokohama, Japan. The company sells ...

VR38DETT The VR is a series of twin-turbo DOHC V6 automobile engines from Nissan with displacements varying from . An evolution of the widely successful VQ series, it also draws on developments from the VRH, JGTC, and Nissan R390 GT1 Le Mans racing eng ...

, and Ford

Coyote The coyote (''Canis latrans'') is a species of canis, canine native to North America. It is smaller than its close relative, the wolf, and slightly smaller than the closely related eastern wolf and red wolf. It fills much of the same ecologica ...

Caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sym ...

and Ford also use PTWA to remanufacture engines.

References

{{Reflist

External links

PTWA internal coating system
*http://www.sae.org/mags/aei/manuf/7624 Metallurgical processes Coatings Plasma physics