Wear behaviour of low-temperature gas nitrided austenitic stainless steel in a corrosive liquid environment

The paper presents the results of an investigation into the wear behaviour of gas nitrided austenitic steel in a corrosive liquid representing conditions appropriate to the manufacture of soft drinks. The layers were obtained by low temperature (400 and 450 °C) gas nitriding and were predominantly composed of a phase known as expanded austenite. Non-treated austenitic stainless steel was used as a reference material and tests in deionised water were also carried out for comparison. The layers were characterised by XRD, optical microscopy, roughness and hardness measurements, and stationary potential tests. Wear and friction tests using an alumina ball as the counter-surface were used to characterise the tribological behaviour. For all samples, the wear performance in the aggressive liquid was superior to that in water, mainly due to a lubricating transfer layer formed on the alumina ball under these conditions.