Two-body abrasion of nitrocarburised steels for hydraulic cylinders

Nitrocarburising has been used increasingly to improve the surface properties of many machine components for tribological applications. In this investigation, two-body abrasion behaviour of different nitrocarburised steels used in the manufacture of hydraulic cylinders has been studied. Three different nitrocarburising processes, namely, salt-bath, gas, and plasma were conducted on five various steel substrates. The substrates were St 52-3, Ck 45, 42 CrMo 4, 30 CrNiMo 8, and X 20 Cr 13. The thickness and porosity of the compound layer were measured using an optical microscopy. The structure of the compound layer was characterised using an X-ray diffractometer and the surface roughness by a stylus profilometer. The surface hardness measurements and hardness profiles were done. The abrasive wear tests were carried out using a pin-on-table machine. The dominant wear mechanisms were identified using scanning electron microscopy. It was found that all nitrocarburising processes used, improved the abrasion resistance of treated steels. In general, the abrasion rate decreased with increasing the hardness and thickness of the compound layer. The most improved treated specimens in terms of improved abrasion resistance were the salt-bath and gas nitrocarburised specimens of the X 20 Cr 13 substrate, whereas plasma nitrocarburised specimens of the St 52-3 and Ck 45 substrates showed the least improvement.