Repair of high-value components in industrial processes characterized by elevated temperature and aggressive environment has become economical with the advent of robust repair processes. Turbine components in gas turbine engines are prime examples. If the cost of the repair process is within 70% of the price of a new part, the repair is considered economical (Underhill, 1985). Generally the economics of repair is assessed by the economic repair factor (ERF), given by

where P and t respectively represent price and life, and the subscripts nw and rp refer to new part and repair process. For coated components both the life and price factors are significantly affected by the degradation and replacement cost of coatings.

Components requiring repair generally have significant exposure in the field with degradation due to such causes as substrate alloy degeneration, oxidation, corrosion, cracking due to thermal and low cycle fatigue, TBC spall, erosion, and foreign object damage. The repair cycle is generally adjusted to coincide with the overhaul of the complete equipment, such as gas turbine engines, to eliminate expenses for additional disassembly. New components may also require repair if they do not meet quality requirements, due primarily to manufacturing aberration and handling damage.