In situ structural evolution of arc-deposited Cr-based coatings

Cr-based coatings were prepared by cathode arc-evaporation technology using N2 and C2H2 as reactive gases. Three compositions were investigated, Cr60N40, Cr41N27C32 and Cr67C33.The present investigation is centred on the structural stability via coatings tempering up to 1000 °C, by in situ X-ray diffraction in protective atmosphere. As-deposited coatings present low order structure with a medium feature size less then 10 nm. The hexagonal β-Cr2N phase, characteristic of binary Cr60N40 coating, was stable up to 900 °C, before recrystallization and grain growth takes place. For Cr41N27C32 film the phase transition varies from the metastable δ-Cr(N,C) to orthorhombic chromium carbonitride Cr3(CxN1 − x)2 phase up to 800 °C and then to chromium carbide phase. No chromium nitride phases were detected in spite of the similar N and C contents after the deposition. The Cr–C coating recrystallizes into a mixture of carbide phases, mainly Cr3C2 and Cr23C6 after 1000 °C annealing treatment.