Multicomponent TiNbCrAl nitride films produced by DCMS and HiPIMS

Sammanfattning: High entropy alloys (HEAs) are made of at least five principal elements in near-equimolar proportions. The vast number of possible alloys and unconventional combinations of properties are the main benefits of HEAs. Ti, Nb, Cr, Al and N were chosen in order to create a hard, corrosion resistant coating with good thermal stability. TiNbCrAl multicomponent nitride thin films with Ti content between 0 to 14.4 at.% were deposited using multi-magnetron reactive high power impulse magnetron sputtering (R-HiPIMS) to investigate the feasibility of this method and to study how the Ti content affects the properties of the film. The samples deposited using reactive direct current magnetron sputtering (R-DCMS) were used as benchmarks. The settings required for near-equimolar composition were fixed, with Ti magnetron power as the only variable. Substrate was grounded and not intentionally heated. The composition of HiPIMS samples was more stable while the DCMS samples had significant fluctuations in Al and N content when varying the Ti target power, and were understoichiometric in nitrogen, (T iCrN bAl)1N1−δ, due to low degree of ionization of N. All crystalline samples had NaCl-type fcc structure. Crystalline DCMS samples were (111) textured, while the higher ionization characteristic for HiPIMS resulted in samples with competitive growth between two growth directions. The energetic particle bombardment caused the columnar structure of the film to be denser and less jagged, while DCMS samples containing Ti were significantly more porous. Denser, harder and stiffer films with significantly higher compressive stress were produced with HiPIMS. The hardness and stiffness were almost linearly dependent on Ti content, with density slightly decreasing as the Ti content increased. Higher Ti content increased the rate of corrosion of the films.