Synthesis and mechanical characterization of CuMoTaWV high entropy film by magnetron sputtering.

Development of high entropy alloys (HEA) films is a promising and cost-effective way to incorporate these materials of superior properties in harsh environments. In this work, a refractory high entropy alloy (RHEA) film of equimolar CuMoTaWV was deposited on silicon and 304 stainless steel substrates using DC-magnetron sputtering. A sputtering target was developed by partial sintering of equimolar powder mixture of Cu, Mo, Ta, W, and V using spark plasma sintering (SPS). The target was used to sputter a nanocrystalline RHEA film with a thickness of ~900 nm and average grain size of 18 nm. X-ray diffraction (XRD) of the film revealed the BCC solid solution with preferred orientation in (110) directional plane. The nanocrystalline nature of RHEA film resulted in hardness of 19 +/- 2.3 GPa and elastic modulus of 259 +/- 19.2 GPa. A high compressive strength of 10 +/- 0.8 GPa was obtained in nano-pillar compression due to solid solution hardening and grain boundary strengthening. The adhesion between the RHEA film and 304 stainless steel substrates was increased on annealing. For the wear test against E52100 alloy steel (Grade 25, 700-880 HV) at 1 N load, the RHEA film showed an average coefficient of friction (COF) and wear rate of 0.25 (RT) and 1.5 (300 oC), and 6.4 x 10-6 mm3/Nm (RT) and 2.5 x 10-5 mm3/Nm (300 oC), respectively. The COF was found to be twice lower at RT and wear rate 102 times lower at RT and 300 oC than 304 stainless steel. This study may lead to the processing of high entropy alloys film for large scale industrial applications.