A study of debris and wear damage resulting from fretting of Incoloy 800 steam generator tubes against AISI Type 304 stainless steel

Wear damage and resulting triboparticles corresponding to fretting of Incoloy 800 steam generator tubes against AISI 304 pads were characterized in experiments performed in air at room temperature in a 90° cross cylinder configuration. Relative displacement amplitudes of 70, 116 and 160 µm under a normal contact load of 35±4 N were considered in experiments performed up to 106cycles. The topography and dimensions of the resulting scars on surfaces were characterized using light microscopy and scanning electron microscopy. The morphology, size and crystal structure of the debris detached during the test were determined by transmission electron microscopy and energy dispersive X-ray spectroscopy. It was verified that gross slip was the prevailing running fretting condition in all cases, while the characteristics of the scar surface layer and the corresponding wear mechanisms were found to depend on the amplitude of the relative displacement. Debris consisted in agglomerations of nano-crystalline oxide particles sized between 5 and 20 nm. The crystal structure of debris was found to depend on the displacement amplitude. For 70 µm and 116 µm, NiO, (Fe,Cr)2O3 and (Ni,Fe)(Fe,Cr)2O4 were found, while the formation of (Fe,Cr2)O3 and (Ni, Fe)(Fe,Cr)2O4 was verified for a displacement amplitude of 160 µm.