Original Article

Improvement of wear resistance of Hardox 400 steel by duplex treatment combining gas carburizing and CrN PVD coating

¹ Laboratory of Mechanics Materials and Processes, ENSIT, Tunis, Tunisia
² Higher Institute of Applied Sciences and Technology of Sousse, Issat Sousse, Tunisia

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Received: 20 August 2025
Accepted: 17 January 2026

Abstract

This study investigates the wear resistance of two different surface techniques applied to Hardox 400 Steel: the direct deposition of chromium nitride (CrN) via physical vapor deposition (PVD), and a duplex strategy where CrN is deposited onto a surface that has first undergone gas carburizing. Our research focuses on the impact of these two treatments on improving the scratch resistance of Hardox 400 steel. A scratch test was performed to evaluate the adhesion of the thin films by identifying the critical loads corresponding to the onset of each damage mode. Adhesion analysis was supplemented with optical microscopy observations. The duplex treatment improves load distribution and reduces coating cracking. Consequently, higher critical load values were achieved. The PVD and duplex-treated layers exhibited Lc1 values of approximately 6 N and 10 N, respectively, which are significantly higher than that of untreated steel (3.17 N), indicating improved resistance to cohesive cracking and enhanced coating adhesion. The best coating adhesion was achieved with the duplex treatment. Multipass scratch tests were conducted to quantify the coefficient of friction, wear volumes, and energy dissipation. The results provided valuable insights into the tribological behavior of the different treatments. It was demonstrated that the duplex system significantly reduces the coefficient of friction by nearly a factor of 3, and decreases the wear volume to approximately 1.56×10⁶ μm³ for the duplex CrN coated sample and 9.53×10⁶ μm³ for the untreated Hardox 400, under an applied load of 20 N.