制备工艺对粉末冶金FeCrNi中熵合金耐腐蚀性能的影响

Effect of preparation process on corrosion resistance properties of powder metallurgy FeCrNi medium entropy alloy

分别采用包套热挤压和热压烧结法制备FeCrNi中熵合金,研究制备工艺对合金组织结构及耐蚀性能的影响。结果表明:采用热挤压工艺制备的FeCrNi中熵合金平均晶粒尺寸为13μm,且存在粗大的退火孪晶,而热压烧结工艺制备的FeCrNi中熵合金晶粒组织更细小,平均晶粒尺寸为6μm。在0.5 mol/L H_(2)SO_(4)+2×10^(-6)mol/L HF溶液中,热压烧结FeCrNi中熵合金表现出更好的耐蚀性,即更高的击穿电位(0.979 V)、更低的腐蚀电流密度(7.68×10^(-6)A/cm^(2))以及更宽的钝化区ΔE(1.011 V)。热挤压FeCrNi中熵合金钝化膜中Cr元素主要以Cr(OH)3形式存在,而热压烧结FeCrNi中熵合金钝化膜中Cr元素主要以Cr_(2)O_(3)形式存在。这是因为热压烧结FeCrNi中熵合金的细晶组织具有高密度晶界,能够为Cr提供更多扩散通道,从而促进钝化膜中Cr_(2)O_(3)的形成,提高钝化膜的稳定性和耐腐蚀性。

FeCrNi medium entropy alloys were prepared by canned hot extrusion and hot press sintering technology,respectively.The effects of preparation process on microstructure and corrosion resistance of FeCrNi alloy were studied.The results show that the average grain size of FeCrNi medium entropy alloy prepared by hot extrusion is 13μm with coarse annealing twins,while the average grain size of FeCrNi medium entropy alloy prepared by hot press sintering is smaller,and the average grain size is 6μm.FeCrNi medium entropy alloy prepared by hot press sintering shows good corrosion resistance in 0.5 mol/L H_(2)SO_(4)+2×10^(-6)mol/L HF solution,that is a higher breakdown potential(0.979 V),a lower corrosion current density(7.68×10^(-6)A/cm^(2)),and a wider passive zoneΔE(1.011 V).Cr element in the passive film of FeCrNi by hot extrusion is mainly in the form of Cr(OH)3,while Cr element in the passive film of FeCrNi by hot press sintering is mainly in the form of Cr_(2)O_(3).This is because the high density grain boundaries of the fine crystal structure provide more diffusion channels for Cr,and then promote the formation of Cr_(2)O_(3)in the passive film,and improve the stability and corrosion resistance of the passive film.