Microstructural evolution and mechanical characterization of a WC-reinforced CoCrFeNi HEA matrix composite

Abstract

High entropy alloys (HEAs) are a relatively new class of material that have shown the potential to exhibit excellent combinations of mechanical properties. Various microstructural modifications have been explored to further enhance their mechanical properties for use in demanding structural applications. The main focus of the present work is an investigation of the effect of adding varying amounts of hard ceramic material (WC) to a tough HEA matrix (CoCrFeNi) by arc melting under an argon atmosphere, including microstructural changes, and evaluation of the WC additions on mechanical properties. X-ray diffraction analysis of the HEA-WC composites showed the presence of both fcc and carbide phases. Scanning electron microscope investigations, including energy dispersive spectroscopy, reveal that chromium diffuses from the matrix and interacts with WC to form an alloyed carbide phase. The amount of alloyed carbide was found to increase with increasing amount of WC addition to the HEA matrix. Mechanical characterization revealed that hardness and yield strength of the HEA-WC composites increase with increasing amount of the carbide phase in the matrix. The hardness of HEA-20wt.% WC sample was found to be as high as 3.3 times (593 HV) the hardness of the base HEA (180 HV), while the yield strength increased from 278 MPa for the base HEA to 1098 MPa for the CoCrFeNi-20 wt.% WC composite. The investigated composites also showed excellent values of ductility (~ 50% strain for CoCrFeNi-10 wt% WC and ~ 20% strain for CoCrFeNi-20 wt% WC). It is therefore believed that ceramic-reinforced high entropy matrix composites have the potential to provide outstanding combinations of mechanical properties for demanding structural applications.

Tungsten Carbide‐Based Materials for Electrocatalytic Water Splitting: A Review

“…The influence of WC particle size on the microstructure and properties of WC‐10CoCrFeNiAl hard alloys was investigated. Moreover, Hussain et al [203] CoCrFeNi‐WC composites were prepared by an arc melting process. The evolution of microstructure and crystal structure were studied as a function of WC weight fraction, together with an investigation of the mechanical properties of the HEA‐ceramic composites.…”

Ceramic-reinforced HEA matrix composites exhibiting an excellent combination of mechanical properties

“…This system has rapid strain hardening characteristic 44 and excellent ductility both at cryogenic and elevated temperatures 45,46 . Different attempts have been made to improve its relatively lower strength (~ 300 MPa) 47,48 , which include grain refinement 25 , multiphase microstructure 49 , precipitation [50][51][52] , and transformation induced plasticity (TRIP) 53 . Grain refinement of the as-cast fcc CoCrFeNi HEA by heavy cold-drawing resulted in an increased strength from ~ 300 MPa 47,48 to 1.2 GPa 25 , but with a loss of ductility from more than 60% to 12.6%.…”

“…Different attempts have been made to improve its relatively lower strength (~ 300 MPa) 47,48 , which include grain refinement 25 , multiphase microstructure 49 , precipitation [50][51][52] , and transformation induced plasticity (TRIP) 53 . Grain refinement of the as-cast fcc CoCrFeNi HEA by heavy cold-drawing resulted in an increased strength from ~ 300 MPa 47,48 to 1.2 GPa 25 , but with a loss of ductility from more than 60% to 12.6%. Multi-phase microstructure developed in CoCrFeNi HEA by the addition Al increased its yield strength to 786 MPa with an elongation of around 22% 49 .…”

“…Addition of ceramic reinforcements to the fcc matrix HEA have also been tried for the development of high entropy composites that can exhibit better combination of strength and ductility. High entropy composites have been developed by vacuum arc melting 44 , mechanical alloying [45][46][47][48]52,53 , spark plasma sintering 46,51,52 , vacuum hot pressing 45 , hot iso-static pressing 47,48 and additive manufacturing 43,50 processes. Carbides, oxides and nitrides such as WC [44][45][46] , Al 2 O 3 47 , SiC 48 , TiC 43,49 , TiN 50 and Y 2 O 3 51 have been used as ceramic reinforcement for the development of HEA composites.…”

“…High entropy composites have been developed by vacuum arc melting 44 , mechanical alloying [45][46][47][48]52,53 , spark plasma sintering 46,51,52 , vacuum hot pressing 45 , hot iso-static pressing 47,48 and additive manufacturing 43,50 processes. Carbides, oxides and nitrides such as WC [44][45][46] , Al 2 O 3 47 , SiC 48 , TiC 43,49 , TiN 50 and Y 2 O 3 51 have been used as ceramic reinforcement for the development of HEA composites. Selection of a suitable HEA matrix and ceramic phase is particularly important to design and develop strong and tough HEA composites.…”