As a result of lightweight construction, contact pressures are rising which necessitates improved wear protection. Hard coatings produced by Physical Vapour Deposition (PVD) like CrAlN are potential options. However, due to their chemical stability the interaction with lubricants for tribofilm formation is strongly limited. Doping CrAlN coatings with Fe to enhance tribofilm formation offers high potential. Iron can catalytically break up hydrocarbons from the lubricant and form amorphous carbon (a-C) tribofilms which can lower wear and friction. CrAlFeN coatings have yet been rarely explored because ferro magnetic properties of Fe disturb the magnetic fields used in magnetron sputtering (MS)-PVD technology. In the present study five CrAlFeN coatings with different chemical compositions were deposited. Wear and friction were analyzed with a pin on disc (PoD) tribometer utilizing a polyalphaolefin (PAO) lubricant. Both, 100Cr6 balls and 42CrMo4 +QT discs were coated. Our findings show that CrAlFeN coatings facilitate the formation of a-C tribofilms. Additionally, pinholes, wear or delamination of CrAlN coating on 100Cr6 counterparts also promotes a similar tribocatalytic effect by exposing the iron substrate, resulting in a-C formation and lowered friction. Note our previous study, where no a-C formation appears in CrAlN system when using Si 3 N 4 counterparts. The results support the hypothesis regarding iron's tribocatalytic role. CrAlFeN coatings can reduce friction by up to 56% and wear by up to 69% compared to the uncoated system. XPS analysis indicates that iron exists in Fe-Fe bonds within CrAlFeN coatings, which could be essential for activating its tribocatalytic function. • Deep material analysis for tribocatalytic CrAlFeN coatings with varying Fe and N content • Proving Fe-Fe bindings via XPS for CrAlFeN coatings deposited with MS-PVD • Demonstration of the tribocatalytic function of CrAlFeN coatings in PVD/PVD systems by cracking hydrocarbons from PAO lubricants forming wear and friction reducing a-C tribofilms • CrAlFeN coatings provide friction reduction up to 56% and wear reduction up to 69% compared to uncoated steel systems
Bobzin et al. (2026) studied this question.