Influence of annealing on microstructures and mechanical properties of arc-deposited AlCrTiSiN coating

Abstract

A AlCrTiSiN nanomultilayered coating, mainly consisting of fcc-AlCrTiSiN solid solution and some hcp-clusters at fcc-AlCrTiSiN nanotwin boundaries, was isothermally annealed at 800–1100 °C. Thermal stability and changes in microstructure were studied carefully to illustrate its thermal dissolution mechanism. A thermal induced transformation of hcp to fcc is observed by emission of partial dislocation at hcp/fcc interfaces when annealed at 800 °C. Furthermore, we observe the onset of decomposition of fcc-AlCrTiSiN solid solution to coherently Al-rich and TiCr-rich fcc domains at 1000 °C via spinodal mechanism, accompanied by the precipitation of semi-coherent hcp-clusters within Al-rich fcc sublayers by nucleation mechanism. This transformation results in a notable hardening due to the refinement of grains and the coherency strains caused by spinodal decomposition and the formation of semi-coherent hcp-clusters. Later, annealing at 1100 °C promotes the dissolution of layered structures by pinching off of hcp sublayers, the transformation of fcc-AlCrTiSiN solid solution to Cr, Cr2N and hcp-AlN particles and the coarsening of hcp-AlN particles, resulting in a notable loss in hardness.