Preparation And Properties Of Wear Resistant High Entropy Alloys

Based on the application potential of high entropy alloy in engineering materials and friction and wear.In order to develop high strength,high toughness and wear-resistant materials as application-orientated,based on thermodynamics principle and size effect to form simple and stable high entropy solid solution,high performance and low cost high entropy alloys with Fe content above 60%,Co,Cr,Ni,Mo content below 40%and Mo content below5%were designed.Fe-Co-Ni-Cr-Mo-C high-entropy alloys were prepared by induction melting and arc melting.The phase composition,microstructure,room temperature mechanical properties and tribological properties of the alloy were systematically explored.In-depth study:(?)the dependence of the phase composition of the alloy and the improvement of its properties on elements,(?)The strengthening and toughening mechanism of the alloy,(?)The friction and wear behavior and wear mechanism of the alloy.It provides the necessary data support for the application of alloy in the field of mechanical equipment.The main conclusions are as follows:(1)The CoCrFeMoNiC_x(x=0,1,2,3,4 and 5)high-entropy alloys were prepared by vacuum induction melting technology.The Co Cr Fe Mo Ni C_xhigh-entropy alloys mainly consisted of a body-centered cubic(BCC)phase.The addition of C caused the lattice distortion,the internal stress and the lattice constant increase,and the interstitial solution strengthening effect is significant.When the content of C content is higher than 2%,small amounts of strip carbides were formed in BCC grains,and the strengthening effect of the second phase is obvious.The mechanical properties of the alloys improved significantly with increase C content,which was attributed to the interstitial solid solution strengthening effect of C and the appearance of small amounts of strip carbides.The mechanical properties of C₅alloy Rockwell hardness,yield strength,compression strength,fracture strain and fracture toughness of C₅alloy are 34.1 HRC,997 MPa,2088 MPa,43.2%and 41.2 MPa·m^0.5respectively.Meanwhile,the wear rates of the alloys decrease continuously with increase C content,showing good wear resistance.The wear mechanisms include abrasive wear,plastic deformation and fatigue wear at room temperature.(2)The Fe_70.8-xCo₁₃Ni₁₂Cr₃Mo_1.2C_x(x=0,0.2,0.4,0.6,0.8,1.0,1.5 and 2.0)high-entropy alloys were prepared by arc melting technique.C₀alloy is composed of a single BCC phase and its chemical composition is uniformly distributed.The addition of the C element activates a specific transformation mechanism.With the increase of C content,BCC phase gradually changes into FCC phase.When the content of C is greater than 1.0%,the interdendritic C,Cr and other elements are enriched,and the properties of the alloy decrease.Under the joint action of interstitial solution strengthening of C atom,transformation of BCC phase to FCC phase and martensitic phase transformation strengthening,C_0.2alloy exhibits super high strength and hardness,good plasticity and toughness,and achieves the unity of strength and plasticity.Excellent mechanical properties make C_0.2alloy show high friction and wear resistance.The abrasive wear,fatigue wear and plastic deformation of the alloy without C doping.When the C content is 0.2?0.4%,the wear mechanism of the alloy is abrasive wear.In addition,the wear mechanisms of other alloys are abrasive wear,fatigue wear and oxidation wear.(3)The arc smelting technology of preparation of Fe_73.8Co₁₃Ni₁₂Cr_xMo_1.2C_0.2(x=0,3,6,12 and 18)high entropy alloys gradually with the increase of the content of Cr for the FCC by BCC phase transition phase.When Cr content is 3%,both the strength and toughness of the alloy are improved by the combined action of Cr atom solution strengthening and martensite strengthening.However,the addition of a large number of Cr atoms makes its solubility in the crystal reach saturation,and the remaining Cr generates a large number of carbides and accumulates at the grain boundary,resulting in cracking at the grain boundary,which reduces the mechanical properties of the alloy.The wear rate of Cr₃alloy is lower than that of most high-entropy alloys,showing excellent resistance to friction and wear.The wear mechanism is abrasive wear.