Influence of sliding speed on modes of material transfer as steel slides against PVD tool coatings

An intermittent sliding test was used in order to study the formation and build-up of tribofilms during intermittent sliding of PVD coated HSS against case hardening steel (20NiCrMo2). Two cutting tool coatings were tested, TiN and AlCrN, and the influence of sliding speed was evaluated. With moderate speed, two tribofilms were formed separately, one consisting of Mn, Si, Al and O on an intermediate layer of Fe and one consisting of Fe, Mn, Cr and O on an intermediate layer of Cr and Mn. At low sliding speeds an uneven transfer of steel occured while high sliding speeds resulted in thermal softening of the substrate leading to coating failure. AlCrN provided better substrate protection at high speeds than TiN did.

► PVD TiN and AlCrN coated HSS were tested in intermittent sliding against 20NiCrMo2.
► Study of formation and build-up of tribofilms and the influence of sliding speed.
► Steel precipitates form an oxidised tribofilm with an interlayer of Fe.
► Oxidised steel constituents with an interlayer of Cr adhered at low temperature/pressure areas.
► AlCrN provided better substrate protection at high speeds than did TiN.