TABLE OF CONTENTS High-temperature metallic and thermal barrier coatings (TBC s) are used for many industrial applications for aggressive environments, as described in Chapter 1. Although a wealth of information exists in the public domain devoted primarily to historical perspectives and the processing and properties of these coatings, literature covering assessment of their application and performance in the field is very scarce, rarely up to date, and in most instances, closely guarded by the industry for competitive business reasons. One of the primary users of high-temperature coatings is the gas turbine engine industry for commercial and military aircraft, industrial power generation, and marine applications. The experience illustrated by selected examples described in this chapter is, therefore, somewhat dominated by these applications. Experience in simulated tests is also included in this chapter because it has many of the attributes of actual field exposure.
Overlay coatings, discussed in detail in sections starting at 6.4, provide the flexibility of tailoring the composition of the coating to the specifics of each application. Typical high-temperature overlay coatings have the general composition of NiCoCrAlY. One of the early methods of deposition of overlay coatings was by the EB-PVD process described in Section 6.6 and in greater detail, for ceramic coatings, in Section 7.5. An example of a coating deposited by this process is PWA 270, which has seen application in Pratt & Whitney-built gas turbine engines. The EB-PVD process relies on the vapor phase to form...
