CVD in Wear-and Corrosion-Resistant Applications

CVD coatings are used extensively in applications requiring resistance to wear and corrosion, often over a wide range of temperature. As mentioned in Ch. 1, these coatings and their substrates can be considered as composites which provide unique combinations of properties. 

Wear and corrosion protection can be provided by the well-established techniques of hard-facing and plating or by surface-modification processes such as bonding, nitriding, carburizing, and ion implantation. The protection these processes afford is adequate in most environments but may fail over a period of time if the conditions are too severe. 

CVD suffers these limitations to a lesser degree and, as a result, is being used increasingly in many industrial applications, particularly those operating in extreme conditions. It is often the best solution to severe problems of erosion, friction, or hot corrosion. A special case must be made forthe coating ofcutting tools, which is amaj or industrial application of CVD and is reviewed separately in Ch. 18. 

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CVD in Wear- and Corrosion-Resistant Applications 441 CVD Nitrides for Corrosion-Resistant Applications... 

The third part identifies and describes the present and potential applications of CVD in semiconductors and electronics, in optics and optoelectronics, in the coating of tools, bearings and other wear- and corrosion-resistant products, and in the automobile, aerospace, and other major industries. 

Chemical vapor deposition (C VD) is a versatile process suitable for the manufacturing of coatings, powders, fibers, and monolithic components. With CVD, it is possible to produce most metals, many nonmetallic elements such as carbon and silicon as well as a large number of compounds including carbides, nitrides, oxides, intermetallics, and many others. This technology is now an essential factor in the manufacture of semiconductors and other electronic components, in the coating of tools, bearings, and other wear-resistant parts and in many optical, optoelectronic and corrosion applications. The market for CVD products in the U.S. and abroad is expected to reach several billions dollars by the end of the century. 

This work reports the development of a polymeric/sol-gel route for the deposition of silicon carbide and silicon oxycarbide thin films for applications such as heat-, corrosion-, and wear-resistant coatings, coatings on fibers for controlling the interaction with the matrix in ceramic matrix composites, or films in electronic and optoelectronic devices. This method, in which the pre-ceramic films are converted to a ceramic coating either by a conventional high temperature annealing or by ion irradiation, is alternative to conventional methods such as chemical or physical vapor deposition (CVD, PVD), molecular beam epitaxy, sputtering, plasma spray, or laser ablation, which are not always practical or cost efficient. 

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