The present work deals with the characterization of the scratch resistance of two different types of coatings, i.e., chromium nitride (CrN) and diamond-like carbon prepared on X42Cr13/W (1.2083) plastic mold tool steel by physical vapor deposition and plasma-enhanced chemical vapor deposition, respectively. Our study focuses on the influence of the duplex treatment, i.e., plasma nitriding + ceramic coating on the scratch resistance of the tool steel. An advanced 3D scratch testing methodology has been used to investigate the coating adhesion and damage mechanism during scratching. The scratch analysis is completed by ball cratering test and micro-Vickers test to determine the thickness and hardness of the coatings. The test results demonstrate that the applied duplex treatment is an unambiguously advantageous surface technological process which manifests itself in higher loadability and lower sensitivity for cracking of the duplex coatings, increasing the critical forces. The scratch resistance of the combined substrate/coating material system is enhanced by the harder substrate material, providing a better interfacial bonding for both types of the ceramic coatings without changing the basic damage mechanisms.

CrN coatings are widely used in the industry due to their excellent mechanical features and outstanding wear and corrosion resistance. Using scratch and ball-on-disk wear tests, the current study deals with the tribological characterisation of CrN coatings deposited onto an X42Cr13 plastic mould tool steel. Two surface conditions of the secondary-hardened substrate are compared—the plasma nitrided (duplex treated) and the un-nitrided (simply coated) states. The appropriate combination of secondary hardening providing the maximum toughness and the high-temperature nitriding of this high Cr steel is a great challenge due to the nitrogen-diffusion-inhibiting effect of Cr. The beneficial effect of the applied duplex treatment is proven by the 34% improvement of the adhesion strength and the 43% lower wear rate of the investigated duplex coatings. Detailed morphological analyses give insight into the characteristic damage mechanisms controlling the coating failure processes during scratching and wearing. For the simply CrN-coated sample, a new type of scratch damage mechanism, named “SAS-wings”, is identified, providing useful information in predicting the final failure of the coating. The tribological results obtained on tribosystems with the investigated high Cr steel/CrN constituents represent a novelty in the given field.