异质结构Ti(C,N)-(Fe)CoCrNi基金属陶瓷及其电化学腐蚀行为

Heterogeneous Ti(C,N)-(Fe)CoCrNi-Based Cermets and Their Electrochemical Corrosion Behaviors

采用(Fe)CoCrNi高/中熵合金雾化粉末原料,制备Ti(C_(0.5),N_(0.5))-20%WC-8%TaC-5%Mo_(2)C-22%FeCoCrNi(A)和Ti(C_(0.5),N_(0.5))-20%WC-8%TaC-5%Mo_(2)C-22%CoCrNi(B)金属陶瓷,采用具有相同黏结金属体积分数的Ti(C_(0.5),N_(0.5))-20%WC-8%TaC-5%Mo_(2)C-12%Co-12%Ni(C)金属陶瓷作为对比合金。电化学实验结果表明,尽管金属陶瓷A和B中存在脱碳相(η相)和微观结构均质性较差等问题,在H_(2)SO_(4)(pH=1)、Na_(2)SO_(4)(pH=7)和NaOH(pH=13)溶液中,相较于无微观组织结构缺陷的金属陶瓷C,金属陶瓷A和B在3种介质中平均自腐蚀电流密度J_(corr)分别降低33%和88%,平均电荷转移电阻Rct分别提高97%和219%,微观组织结构缺陷不影响其耐蚀性改善;在H_(2)SO_(4)中,金属陶瓷B的J_(corr)降低89%,Rct提高750%,CoCrNi中熵合金黏结金属能显著改善金属陶瓷在强腐蚀性介质中的耐蚀性。从高、中熵合金本征特性,合金体系润湿性等视角分析了金属陶瓷A和B中η相形成伴随的异质结构形成机理。

Ti(C_(0.5),N_(0.5))-20%WC-8%TaC-5%Mo_(2)C-22%FeCoCrNi(A)and Ti(C_(0.5),N_(0.5))-20%WC-8%TaC-5%Mo_(2)C-22%CoCrNi(B)cermets were prepared by using(Fe)CoCrNi high and medium entropy alloy atomized powders,respectively.Ti(C_(0.5),N_(0.5))-20%WC-8%TaC-5%Mo_(2)C-12%Co-12%Ni(C)with the same binder metal volume ratio was used as the reference alloy.The electrochemical experiment results show that despite the presence of decarburization phase(ηphase)and poor microstructure homogeneity,compared with the cermet C without microstructure defects,in H_(2)SO_(4)(pH=1),Na_(2)SO_(4)(pH=7),and NaOH(pH=13)solutions,the values of average self-corrosion current density(J_(corr))for cermets A and B are decreased by 33%and 88%,and the values of average charge transfer resistance(Rct)are increased by 97%and 219%,respectively.The defects of microstructures do not affect the improvement of corrosion resistance.In the H_(2)SO_(4)solution,J_(corr)for cermet B is decreased by 89%,and Rct is increased by 750%.The corrosion resistance of cermets in extremely corrosive media can be significantly improved by using CoCrNi medium entropy alloy as the binder metal.The formation mechanism of heterogeneous structure accompanied by the formation ofηphase in cermets A and B is discussed from the perspective of intrinsic properties of high and medium entropy alloys and the wettability of the alloy system.