A Comparison of EBPVD and Thermal Spray Thermal Barrier Coating Systems

摘要

Zirconia thermal barrier coatings have been produced by both thermal spray (TS) and electron beam physical vapor deposition (EBPVD). TS (usually plasma spray) offers low thermal conductivity and wide variations in microstructure including low to high density, vertically macrocracked or segmented, and monolithic, multilayered or continuously graded. Its disadvantages include a rough exterior surface as-deposited and a relatively rough interface with its metallic undercoat. EBPVD coatings have a columnar microstructure that provides substantial resistance to thermal shock, a smooth exterior surface, and do not require a rough interface with most metallic undercoats. Both are essentially line-of-sight deposition processes. The capital and operating costs of EBPVD deposition processes are typically substantially higher than those of TS. There is controversy over the relative thermal shock/thermal fatigue resistance of the two types of coating as well as their life cycle costs. This brief comparison will consider these and other factors important to the selection of the best coating system for a given application.