Diffusion, defects and understanding the growth of a multicomponent interdiffusion zone between Pt-modified B2 NiAl bond coat and single crystal superalloy
Diffusion, defects and understanding the growth of a multicomponent interdiffusion zone between Pt-modified B2 NiAl bond coat and single crystal superalloy
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DOI：
10.1016/j.actamat.2020.04.016
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发表时间：
2020-08-15
期刊：
影响因子：
9.4
通讯作者：
Paul, Aloke
中科院分区：
文献类型：
--
作者：
Esakkiraja, Neelamegan;Gupta, Ankit;Paul, Aloke
在B2-Ni（CoPt）Al体系中，采用伪二元和伪三元扩散偶方法，确定了与组分相关的扩散系数，这在满足条件的四元非均匀材料中是不可能实现的。基于热力学细节选择产生理想/接近理想扩散分布的端元组成。Co的存在降低了Ni和Al的伪二元互扩散系数，而Pt的存在提高了伪二元互扩散系数。伪三元互扩散系数表明，在Pt的存在下，主要的互扩散系数显着增加。交叉互扩散系数的边际变化证实了组件之间的扩散相互作用的微小变化。的热力学驱动力表现出相反的趋势，相对于组合物的相互扩散系数的变化相比，主张占主导地位的作用的Pt（Co）引起的修改点缺陷浓度。基于DFT的计算表明，Pt合金化增加了Ni空位浓度，降低了三重缺陷扩散机制的激活能。这些发现解释了由于Pt的添加，B2-Ni（Pt）Al粘结涂层和单晶高温合金Rene N5之间的互扩散区的厚度增加。此外，电子探针和透射电镜分析显示，难熔元素富集沉淀的生长。(C)2020 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
Composition-dependent diffusion coefficients are determined in B2-Ni(CoPt)Al system following the pseudobinary and pseudo-ternary diffusion couple methods, which would not be possible otherwise in a quaternary inhomogeneous material fulfilling the conditions to solve the equations developed based on the Onsager formalism. The end-member compositions to produce ideal/near-ideal diffusion profiles are chosen based on thermodynamic details. The pseudo-binary interdiffusion coefficients of Ni and Al decrease in the presence of Co but increase in the presence of Pt. The pseudo-ternary interdiffusion coefficients indicate that the main interdiffusion coefficients increase significantly in the presence of Pt. Marginal changes of the cross interdiffusion coefficients substantiate a minor change of the diffusional interactions between the components. The thermodynamic driving forces show opposite trends with respect to composition as compared to the changes of the interdiffusion coefficients advocating a dominating role of the Pt(Co)-induced modifications of point defect concentrations. DFT-based calculations revealed that Pt alloying increases the Ni vacancy concentration and decreases the activation energy for the triple defect diffusion mechanism. These findings explain the increase in the thickness of the interdiffusion zone between the B2-Ni(Pt)Al bond coat and the single crystal superalloy Rene N5 because of Pt addition. Furthermore, the EPMA and TEM analyses reveal the growth of refractory elements-enriched precipitates. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.