Effect of High Ion Irradiation on the Structure, Properties and High Temperature Tribology of Nanoscale CrAlYN/CrN Multilayer Coating Deposited by HIPIMS-HIPIMS Technique

The high degree of ionisation of the sputtered particles in High power impulse magnetron sputtering (HIPIMS) discharge was utilised to deposit very dense nanoscale multilayer CrAlYN/CrN coatings. These newly developed coatings are designed to meet the demands for high oxidation and wear resistant coatings of light weight materials such as gamma-TiAl alloys for future applications in aerospace and automotive engines. The coatings were produced by a HIPIMS-HIPIMS methodology in which HIPIMS was employed for adhesion enhancement surface pre-treatment as well as for coating deposition in combination with standard unbalanced magnetron sputtering (UBM). TEM studies revealed extremely sharp interfaces between the individual layers in the nanolaminated material and almost no layer waviness. The coatings exhibited low friction and wear coefficients (K-c) at ambient and elevated temperatures of 300 and 650 degrees C. Quasi-isothermal oxidation tests carried out at 850 degrees C for exposure time of 2 000 h exhibited a lower mass gain of HIPIMS-HIPIMS coatings by a factor of 2 and 6 as compared to the HIPIMS/UBM deposited coatings and uncoated gamma-TiAl substrate respectively.