Study Of The Wear And Corrosion Resistance Of WC-HEA Cemented Carbide In Seawater Media

Equipment or parts operating in complex and variable marine environments are often subject to the combined effects of wear and corrosion,which requires materials with not only high hardness and wear resistance,but also excellent resistance to the corrosive properties of seawater.WC cemented carbide is the material of choice for equipment operating in the marine environment due to its excellent wear resistance,but traditional WC cemented carbide is often difficult to fully meet the material requirements for equipment operating in the marine environment,such as WC-Co cemented carbide with metal Co as the bonding phase has high hardness,but poor corrosion resistance.WC-Ni cemented carbide with metallic Ni as the bonding phase has excellent corrosion resistance,but poor mechanical properties.The CoCrFeNi high-entropy alloy（HEA）has a series of advantages such as high hardness,corrosion resistance and good wear resistance,etc.The WC cemented carbide prepared by using it as the bonding phase is expected to meet the requirements of equipment serving in the marine environment.In this paper,five CoCrFeNi,CoCrFeNi Mo,CoCrFeNi Ti,CoCrFeNi Al and CoCrFeNi Mn high-entropy alloy powders were prepared by real-air atomization method,and the morphology and phase structure of the powders were analyzed.On this basis,the five WC-based cemented carbides were prepared by vacuum hot-pressure sintering using the above high-entropy alloy powders as the bonding phase,and the microstructure,mechanical properties,wear resistance,corrosion resistance and wear-corrosion coupling resistance in simulated seawater solutions were investigated in comparison with WC-Ni alloys.The main conclusions obtained from the paper are as follows:1.The morphology and phase structure of the CoCrFeNi high-entropy alloy powders were analysed.The results show that the five CoCrFeNi high-entropy alloy powders prepared by real-air atomisation are all spherical or nearly spherical in shape,and the content of alloying elements in the powders is close to the isoatomic ratio;CoCrFeNi Mo and CoCrFeNi Ti are in FCC+BCC phase structure.2.A comparative study of the surface morphology and mechanical properties of WC-Ni and five WC-HEA cemented carbides was carried out.The results show that Ti WC₂hard phase is produced in WC-CoCrFeNi Ti and Al₂O₃ in WC-CoCrFeNi Al.The WC grain size of the five WC-HEA is smaller compared to that of the WC-Ni carbide.The relative densities of the WC-HEA carbides are lower than those of WC-Ni under the same sintering process,except for the WC-CoCrFeNi alloy.the hardness and fracture toughness of the WC-HEA carbides are higher than those of WC-Ni,with WC-CoCrFeNi Ti having the highest hardness（2292.9 HV）and the WC-CoCrFeNi Mo alloy having a fracture toughness value of(10.981 MPa-m^1/2)was the highest.3.The frictional wear resistance of WC-Ni and five WC-HEA cemented carbides under dry friction conditions was investigated.The results show that WC-HEA has a lower friction factor and a shorter friction run-in period than WC-Ni carbide,and its wear rate is approximately two orders of magnitude lower than that of WC-Ni.Among them,WC-CoCrFeNi Al has the best wear resistance and WC-CoCrFeNi Ti is the next best.The wear mechanism of all six alloys is mainly abrasive wear and oxidation wear.4.The corrosion resistance of WC-Ni and five WC-HEA cemented carbides in 3.5%Na Cl solution was compared.The results show that the corrosion resistance of the WC-HEA carbides in 3.5%Na Cl solution is better than that of the WC-Ni alloys,except for WC-CoCrFeNi Mo,where the WC-CoCrFeNi Ti alloy has the best corrosion resistance,followed by WC-CoCrFeNi.The corrosion surfaces of the five WC-HEA carbides are denser compared to WC-Ni,and the formation of various oxides（WO₃,Ni O,Ti O₂,Fe₂O₃and Cr₂O₃ etc.）on the corrosion surfaces of the alloys contributes to the corrosion resistance of the alloys.5.Electrochemical friction wear experiments with simulated seawater as the medium were carried out to investigate the properties of WC-Ni and WC-HEA cemented carbides under coupled wear-corrosion action by comparing the results with those of wear and single corrosion under dry friction conditions.The results show that the six alloys have an increased tendency to corrode,an increased corrosion rate and a reduced corrosion resistance under the coupled wear-corrosion effect compared to the single corrosion condition.The six alloys exhibited lower friction factors and higher wear rates in simulated seawater compared to dry friction conditions.The wear-corrosion coupling not only intensifies the wear of the alloys,but also reduces the corrosion resistance of the alloys.Among them,the WC-CoCrFeNi Ti alloy has the best resistance to the wear-corrosion coupling effect.