Proton irradiation, tribological and corrosion characteristics of Fe-Ni based ODS alloys

In the current study, Fe-42% Ni-2% Y2O3-2%Ti (2Ti) and Fe-42% Ni-2% Y2O3-2%Ti-2%Al (2AlTi) (All in wt%) invar-based alloys were investigated thoroughly under extreme environmental conditions including wear resistance, proton irradiation characteristic, and corrosion behavior. Both the compositions were developed by mechanical alloying (MA) followed by spark plasma sintering (SPS). The phase evolution characteristics and microstructural features of sintered samples were investigated through x-ray diffraction (XRD), and electron backscatter diffraction (EBSD) and TEM analysis. The influence of proton irradiation damage on micrographic features as well as on hardness values of the sintered samples was studied in detail to understand the roles of grain size and complex dispersoids on irradiation damage. Grain boundary seems to play as radiation sinks, whereas regions of dispersoids are found to remain unaffected by proton irradiation. A detailed tribological study was conducted on the sintered samples at 20, 300, and 500 degrees C to understand the effect of temperature, and correlation between the microstructural constituents and wear mechanisms. Analysis of wear data revealed that material loss is gradually reduced with increase in temperature, especially in the 2AlTi sample, due to fast evolution of Al-containing glossy oxide layer providing a better lubricating film to prevent from further wear. Wear mechanism is gradually changed from adhesive to abrasive wear with increase in temperature due to the development of finer glossy protecting oxide debris. In contrast to the wear behaviour, potentiodynamic polarization test analysis of the sintered samples (conducted in an electrolyte of 3.5% NaCl) revealed that the Al containing alloy showed rigorous degradation (huge pitting) due to the presence of coarser Al-rich Y-Al-O dispersoids in fine grained matrix.