Abstract
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.
