Effect of Ti content on achieving development of mechanical properties and wear resistance of CoCrFeNiMoTix high entropy alloy

Abstract

To achieve the synergy among density, strength, ductility, wear performance and thermal stability, a series of newly developed CoCrFeNiMoTix (x = 2 and 16.666 at. %) high entropy alloys (HEAs) via multiple phases nano crystalline structure were successfully fabricated using mechanical alloying (MA) following by spark plasma sintering (SPS). The results demonstrated that the SPSed Ti2-HEA and Ti16.6-HEA have a multiple phases structure consisting of FCC structure (Ni-type as a major phase), two types of BCC structure (Mo-type and Ti-type), topologically close packed (TCP) phases (laves, sigma (σ) and R phases) and geometrically close packed (GCP) phase (L12 precipitates). The micro hardness, strength and specific strength were increased from 711 HV, 1770 MPa and 197 MPa.Cm3/g for the Ti2-HEA to 817 HV, 1830 MPa and 236 MPa.Cm3/g for the Ti16.6-HEA, respectively, which were affected by more percentages of precipitates, intermetallic and BCC phases. Besides, fracture strain, coefficient friction, wear rate and the surface roughness were decreased from 16%, 0.19, 4.9*10−4 mm3 N−1 m−1 and 54.2 for the Ti2-HEA to 14.5%, 0.17, 2.7*10−4 mm3 N−1 m−1 and 31.6 for the Ti16.6-HEA. The ultimate shear strength (USS) values at 300 °C, 400 °C, 500 °C and 600 °C were increased from 960 MPa, 820 MP, 646 MPa and 24 MPa for the Ti2-HEA to 1180 MPa, 1010 MP, 802 MPa and 94 MPa for the Ti16.6-HEA, respectively. The Ti16.6-HEA illustrated higher thermal stability at all temperatures, where the USS slightly was decreased from 300 °C to 500 °C with a sudden drop at 600 °C.

Keywords

• High entropy alloy
• Ti content
• Microstructure evolution
• Compressive properties
• Shear deformation behavior
• Wear performance