It is difficult for engineers and scientists to remain up to date on the wide variety of surface engineering technologies available for product and process design, to solve maintenance problems, etc. This paper provides a brief overview of several of the major types of surface processes and resulting coatings or other surface treatments. It is intended only to provide an elementary introduction to serve as a background for further inquiry by the reader or to assist those not familiar with a given field to more easily understand other presentations in this conference session. The technologies considered include thermal spray, physical vapor deposition, and chemical vapor deposition.

Industrial demands for higher quality, yet lower cost thermal spray coatings have driven the development of highly automated and fully integrated thermal spray systems. These systems include computer control of the powder, gas, electrical power, and cooling fed to the spray device, auxiliary cooling of the part, and motion of the part spray device. The subsystems may include closed-loop control of particular parameters such as the powder feed rate. More fundamental closed-loop or "intelligent" processing systems are under development. A key element in such systems is the ability to sense critical parameters that are indicative of the coating's properties in such a manner that changes in the process can be made to maintain its properties while the coating is being deposited. For example, it is widely recognized that the temperature, velocity, and size distribution of the powder particles during flight are largely responsible for the properties of the resultant coating. A variety of sensor systems have been developed recently that can measure one or more of these properties. At least one such system is capable of measuring all three parameters for the full cross section of the spray. Computer controls, closed loop systems, and intelligent processing cannot compensate for poorly designed, manufactured, or maintained equipment. Nor can they compensate for unsatisfactory preparation of the surface, feedstock (powder, gas, power), finishing equipment or materials, or training of operators. Sufficient attention to all of these factors may even make the investment in some more sophisticated systems questionable for some applications. This paper will attempt to provide an overview of the currently available highly automated and integrated thermal spray systems used for intelligent processing and consider some criteria for its selection and use.

Thermal spray coatings are very effective in combating wear and corrosion in many applications. New thermal spray processes and coating compositions continue to be developed with concomitant improvements in the performance of the coatings and their use in new applications. Nonetheless, the thermal spray coatings are not without competition from other coating and overlay processes and materials. This brief review considers the microstructures and the wear and corrosion resistance of a number of alternative coatings to thermal spray coatings, including physical vapor deposition, chemical vapor deposition, electroplating, autocatalytic, and laser cladding.

Thermal spray coatings are widely used for erosion resistance, but the relationship between the microstructure of the coatings and their erosion resistance is not well understood. In this paper the performance of several commonly used coatings at ambient and elevated temperatures is reviewed in light of the coatings' structure and compared with a new coating. Two high temperature industrial applications, solid particle erosion in steam turbines and alumina-based erosion have been chosen to illustrate the significance of a coating's structure on its performance.

Fiber-reinforced polymer composites are an important class of structural materials, offering high strength-to-weight ratios and high rigidities. For many applications, however, their wear resistance is less than desirable. Wear-resistant thermal spray coatings have the potential to improve the surface properties of fiber-reinforced polymer composites, although some require the application of a bond coat to achieve sufficient adhesion. The present study was conducted to find acceptable bond coat materials and compare their performance. Materials such as polyamides, polyimides, polyether-ether-ketone, or simply aluminum or nickel were found to be suitable bond coats for many composite substrates.