Micro-abrasive Wear Resistance Of Low-temperature Plasma Carburized Martensitic Stainless Steel

The effect of low-temperature plasma carburizing treatment on the micro-abrasive wear resistance of AISI 420 steel was investigated by mean of a CSM Calowear ball-cratering equipment. Carburized samples were treated at temperatures of 350, 400, 450 and 500°C for a fixed time of 12 h, using a gas mixture containing 99.5% (80% H2+20% Ar)+0.5% CH4. Micro-scale abrasive wear tests were conducted with a 25.4 mm AISI 420 steel sphere, using an abrasive suspension of alumina (Al2O3) with particle size of 1 ?m (abrasive concentration of 0.11 g/cm³). The contact normal force, abrasive flow and ball rotation speed were fixed at: 0.5 N, 0,2 drop/s, and 120 rpm. The wear craters were analyzed using a confocal laser microscope, Olympus OLS 3000. The wear analyses were performed for test times of: 30, 60, 90, 120, 180, 360, 540, 720 and 900 s (equivalent sliding distance: 0.84, 1.68, 2.52, 3.36, 5.04, 10.09, 15.14, 20.19 and 25.23 m, respectively). The results indicate that the wear coefficient in the outer layer and in the diffusion layer are different, being lower in the latter. It was also verified that the wear coefficient on the outer layer region decreases with increasing treatment temperature in the range of 350 to 450 °C, and increase again for 500ºC. The diffusion layer wear coefficient is similar for all the carburized samples. Finally, for all studied conditions, the analysis of the wear craters surface indicates the occurrence of grooving and micro-rolling abrasion wear modes.