Characterisation of subsurface oxidation damage in Ni based superalloy, RR1000

Isothermal oxidation of the Ni based superalloy, RR1000, has been performed at 700, 750 and 800°C for exposure periods up to 2000 h. A chromia external oxide scale with an outer layer of rutile was formed together with extensive internal oxidation of aluminium, both intragranularly and intergranularly. The internal oxidation was associated with a deeper γ′ particle free zone. Extensive metallographic measurements of both the depth of internal oxidation and of the γ′ particle free zone were made. The kinetics in each case approximated well to parabolic. Possible rate controlling processes are discussed.