Apparatus and method for electric spark peening of gas turbine components

Peening provides compression of component surfaces in order to create residual surface compressions to resist crack propagation in components such as aerofoils. Previously peening techniques have had problems with respect to achieving adequate treatment depths, speed of treatment and with respect to effectiveness. By the present method arrangement an electrical conductor in the form of a wire is subject to electrical pulses to cause evaporation and subsequent breakdown with high power ultrasound (HPU) propagation in a volume of dielectric fluid towards a component and so peening. The electrical conductor ensures that there is limited possibility of electrical discharge to the component surface while the positioning of the wire relative to the surface can be adjusted to achieve best effect particularly if reflector devices are utilized to concentrate (HPU) pulse presentation to the component. Furthermore, the component can be surface treated in order to provide protection from potentially damaging emissions from evaporation and electrical discharge to the wire.