The role of frequency on fretting corrosion of Alloy 690TT against 304 stainless steel in high temperature high pressure water

In high temperature high pressure (HTHP) water, the role of frequency in fretting corrosion behavior and mechanism of Alloy 690TT against Type 304 stainless steel were investigated. Results indicated that wear mechanisms of delamination, material transfer and oxidation collectively dominated the fretting corrosion behavior. The delamination was related to pure mechanical wear to produce fresh surface exposed to HTHP water for oxidation, resulting in the increase of wear depth and volume. The increasing frequency played little role in oxide type of worn surfaces, which consisted of (Ni,Fe)(Fe,Cr)(2)O-4 and Cr2O3. However, it enhanced the maximum thickness of oxide film in the worn surface. The increasing frequency resulted in the acceleration of the formation of nanostructured tribologically transformed structure (TTS) layer because it could aggravate the plastic deformation and increase the contact temperature for dynamic recrystallization. The increasing frequency accelerated the escape of the ultra-fine grained wear debris, which originated from not only the damage of TTS layer but also the crushed oxide particles generated in the contact gap.