We have a problem related to corrosion of a part called a Torsion bar (cylindrical shape with length of 54mm and dia 0.57mm at cente and 3.15 mm at the ends) which is made out of Elgiloy material. It is supposed to work for 4e9 torsional cycles during its lifetime with a total torsional stress of 1.4e6kg/cm2. The part is fabricated by the process of turning, grinding spark erosion and lapping followed by chemical polishing of a cold worked Eligiloy rod of 4mm diameter After achieving the shape the part should be subjected to Heat treatment as per the following specification Temperature – 527 C Slope – 15 C per min (max) Time Duration - 5 hrs. Atmosphere – Vacuum / inert Cooling – natural cooling under vacuum condition. During Heat treatment a present batch of elgiloy bars underwent an anmolous heat treatment as per following pattern Temperature - 527C Slope – 15 C per min (max) Time Duration – 2 hrs. Atmosphere – Vacuum / inert Cooling – natural cooling under vacuum condition Problem observed is as follows: After the Heat Treatment it is observed that the colour of the bar has changed from basic elgiloy colour to brown colour. Earlier we have not noticed such problem. Kindly clarify the following points. a) Whether the colour change is due to oxide formation? If so what could be the possible oxide (Chromium oxide, Nickel oxide, Iron oxide or any other oxide)? b) Whether the oxide formation may be up to core or only on surface? c) Whether the colour change can affect the fatigue life of the bar which is expected to survive repeated Torsional stress cycle to an order of 4e9 cycles. d) If the oxide formation is on the surface, is there any method to remove the oxide layer without effecting the fatigue and functional requirements.