| CoCrFeNi high-entropy alloy(HEA)has an excellent combination of strength and ductility.In addition,its excellent mechanical properties can be maintained under extreme temperature conditions.It is expected to be used as a new high-performance metal material.But its wear resistance needs to be improved.In this study,the CoCrFeNi HEA and carbon-doped CoCrFeNi-based HEA were prepared by arc melting technology,and homogenization heat treatment,forging and forging after annealing were performed to change the microstructure of the alloys.After selecting reasonable test parameters,the effect of microstructure on the friction and wear properties of CoCrFeNi HEAs and the effect of carbides on the friction and wear properties of carbon-doped CoCrFeNi-based HEAs was explored.For the CoCrFeNi high-entropy alloy,the exploration of the test parameters shows that under the conditions of a load of 6.5 N and a speed of 300 r/min,the abrasion loss is moderate,which is convenient for analysis and testing,and is suitable for subsequent test parameters.The investigation of the friction and wear properties of CoCrFeNi HEAs shows that for the homogenized sample,the grains are equiaxed.The hardness,average friction coefficient and wear rate of homogenized samples is 174 HV,0.64 and 5.49×10-4 mm3/(N·m)respectively.After forging,the grains are elongated and appear fibrous.The hardness and average friction coefficient of forged alloys is 276 HV and 0.59.The wear rate of the sample after forging is 35%lower than that of the homogenized sample.A large number of twins form inside the grains under the treatment of annealing after forging.In this state,the hardness and average friction coefficient of the sample is 163 HV and 0.62.The wear rate of the sample decreases by 26%compared with that of the homogenized sample.The investigation of the friction and wear properties of carbon-doped CoCrFeNi-based HEAs shows that the hard phase is the M23C6 type carbide.After homogenization heat treatment,carbides exist in needle-like and granular shapes.The hardness ranges from 240 HV to 275 HV.The average friction coefficient ranges from 0.64 to 0.70 and the wear rate ranges from 3.70×10-4 mm3/(N·m)to 5.27×10-4 mm3/(N·m).After forging,the carbides are broken.The hardness ranges from 340 HV to 381 HV.The average friction coefficient ranges from 0.59 to 0.65 and the wear rate ranges from 3.27×10-4 mm3/(N·m)to 4.81×10-4 mm3/(N·m).Annealing after forging makes the carbide spheroidized.In this state,the hardness ranges from 195 HV to 266 HV.The average friction coefficient ranges from 0.56 to 0.58 and the wear rate ranges from3.08×10-4 mm3/(N·m)to 3.63×10-4 mm3/(N·m).For CoCrFeNi HEAs,the main wear mechanisms of the alloy under different conditions are two-body abrasive wear and oxidation wear.Forged alloys have the best wear resistance and the highest average friction coefficient due to the highest hardness.When the carbon content is 1.3 at%,the CoCrFeNi-based HEA has the best wear resistance and the wear mechanism is two-body abrasive wear and oxidative wear.When the carbon content is 3.5 at%and 5.4 at%,the wear mechanism of the CoCrFeNi-based HEA is two-body abrasive wear,oxidative wear and three-body abrasive wear.The obstacle of carbides to the grinding ball makes the average friction coefficient increase with the increase of carbon content after homogenization heat treatment and annealing after forging.The alloy has the most excellent wear resistance after forging and annealing.Firstly,the toughness increases after annealing so that the ability of the matrix to resist crack growth is enhanced.Secondly,the distribution of carbides is more uniform and spheroidization of carbides occurs so that the ability of carbides to cut the substrate is weakened. |
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