Erosion-wear and intergranular corrosion resistance properties of AISI 304L austenitic stainless steel after low-temperature plasma nitriding

Abstract

In this paper, AISI 304L austenitic stainless steel has been subjected to plasma nitriding at 673 and 681 K lasted for 6, 18, 24, and 36 h. The morphology, microhardness, phase, and microstructure evolution of the nitrided layer were studied. Not only an expanded austenitic phase (γN) but also Cr-nitrides were formed in the nitrided layer. Transmission Electron Microscopy (TEM) study showed the formation of amorphous and nanocrystalline phases in the surface layers of the samples. The erosion-wear and intergranular corrosion (IGC) resistance behaviors of the nitrided samples were studied in detail. As compared to the non-nitrided sample, the erosion-wear resistance of the nitrided layer at normal impact angle doubles after nitriding at 673 K for 6 h, as a result of the formation of γN phase. Degree of sensitization (DOS) of IGC is gradually enhanced with the increase of nitriding time as indicated by a double loop electrochemical potentiokinetic reactivation (DL-EPR) measurement. This is assigned to the nanostructuring and to the Cr-depletion in the areas adjacent to the Cr-nitrides.