AbstractElectrodischarge machining (ED M) reduces the thermal fatigue resistance compared to conventional machining. The most common corrective treatments employed are electropolishing, shot peening, and the melonite nitrocarburising process, all of which can improve the thermal fatigue resistance. This improvement is attributed to a smoother surface and the elimination of the overtempered layer as well as the removal of the brittle recast layer. The corrosion resistant oxide layer on the melonite treated specimens also has beneficial effects on the thermal fatigue behaviour. The Charpy V notch impact energy of ED electropolished and shot peened samples is slightly higher than that of conventionally machined specimens. However, melonite treatment lowers the impact energy of the specimens compared to conventionally machined samples.