Torsional Fretting Wear Behavior of Duplex DLC Coatings Deposited on Ion Nitriding Treated LZ50 Steel

Abstract

Duplex ion nitriding/DLC coatings were prepared on LZ50 steel. Characterizations were detected by scanning electron microscopy, atomic force microscope, Raman spectroscopy, dynamic ultra-micro hardness tester, and profilometer. The torsional fretting wear behaviors of DLC coatings and substrate LZ50 steel against GCr15 steel ball in dry conditions were studied under angular displacement amplitudes within a range of 0.1°–5°, constant normal load of 50 N, and rotational speed of 0.8° s−1. DLC coatings presented dense structure and high hardness. Compared with the substrate, DLC coatings removed the mix fretting regime and shifted the slip regime to low angular displacement amplitudes. The friction torques of DLC coatings were lower than that of the substrates. In the partial slip regime, the damage of DLC coatings was low. In the slip regime, the damage mechanism combined with delamination, abrasive wear, and graphitization. The DLC coatings exhibited good capability for anti-torsional fretting damage.