A 5 µm thick nanoscale multilayer CrAlYN/CrN coating was produced by high power impulse magnetron sputtering (HIPIMS) substrate pretreatment and subsequent coating deposition by unbalanced magnetron sputtering. HIPIMS pretreatment resulted in high adhesion due to local epitaxial growth on large substrate surface areas. Isothermal heat-treatment for 1 h at various temperatures up to 1 000 °C was carried out, X-ray analysis and cross-sectional transmission electron microscopy revealed a coating structure stable up to 900 °C. Above 900 °C, the thin film decomposed into Cr2N and hcp-AlN, resulting in stress relaxation and reduced hardness, a dense and protective duplex-oxide with an Al-rich outer and a Cr-rich inner oxide layer formed at 1 000 °C.
- Plasma etching
- Transmission electron microscopy