A comparative study of duty cycle and argon / methane flow ratio effect on the tribological behavior of DLC coatings over nitrided Astaloy Mo-based steel

Abstract

Surface properties of Astaloy Mo-based steel were enhanced by using DLC deposition. The specimens were formed by double-sided compaction and heated for 30 min at 1393 K, in the NH3 atmosphere. Following this, the plasma nitriding process was applied to improve the adhesion of the DLC coating. Afterward, the DLC coating was performed by Pulsed DC PACVD. Surface characteristics were studied by changing the duty cycle and the Argon/Methane flow ratio. The reciprocating method was carried out to evaluate wear behavior. Field emission scanning electron microscopy equipped with EDS and Raman spectroscopy, hardness tester, nanoindentation test and surface roughness tester were used to evaluate the chemical structure, wear mechanisms of DLC coatings. This study proved that hardness reached up to 12.2 ± 1.11 GPa and the wear behavior was enhanced significantly by the DLC coating deposition. The mass loss increased with a rise in the duty cycle. Increasing the Argon/Methane ratio from 4:1 to 6:1 caused a decrease in the mass loss of DLC coatings. Burnishing, pulling out and adhesive wear were the dominant mechanisms.