Formation behavior of in-situ NbC in Fe-based laser cladding coatings
Formation behavior of in-situ NbC in Fe-based laser cladding coatings
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DOI：
10.1016/j.matchar.2016.08.005
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发表时间：
2016-09-01
影响因子：
4.7
通讯作者：
Qin, Cha
中科院分区：
文献类型：
--
作者：
Cao, Ya-bin;Zhi, Shi-xin;Qin, Cha
原位NbC在铁基复合涂层中以花瓣状、多面体状、枝晶状、网络状和颗粒状等形式存在。在凝固的早期阶段被液-固界面吞没的NbC相具有小的尺寸并且作为颗粒分布在基体中。多面体和花瓣状NbC相演变从NbC颗粒，通过一个长期和快速的增长过程中没有被界面吞没。树枝状和网状NbC相作为在凝固的终端阶段形成的共晶物质存在。由于基体金属的稀释作用，涂层中的Nb含量大大低于粉末中的Nb含量。Nb的稀释率接近相应涂层的稀释率。涂层中并非所有Nb都能与C反应生成NbC。NbC和固溶Nb的含量主要取决于涂层中的Nb含量，而不是粉末中的Nb含量。当涂层中Nb含量和实验参数在一定范围内变化时，NbC中Nb含量和溶解Nb含量均随涂层中Nb含量的增加而线性增加。降低涂层中的Nb含量可以促进NbC相从网络和/或枝晶转变为颗粒。涂层的显微硬度随NbC含量和固溶Nb含量的增加而增加，但NbC的形貌对涂层的显微硬度无显著影响。(C)2016 Elsevier Inc. All rights reserved.
In-situ NbC exists as petals, polyhedrons, dendrites, networks, and particles in Fe-based composite coating. NbC phases engulfed by the liquid-solid interface at early stages of solidification exhibited small sizes and are distributed in the matrix as particles. Polyhedral and petaloid NbC phases evolve from NbC particles that were not engulfed by the interface through a long and rapid growth process. Dendritic and network NbC phases are present as eutectic substances that form in the terminal stages of solidification. The Nb content in the coating is considerably lower than that in the powder because of the dilution effect of base metal. The dilution rate of Nb is close to that of the corresponding coating. Not all Nb in the coating can react with C to form NbC. The content of NbC and dissolved Nb mainly depends on Nb content in the coating instead of that in the powder. Both Nb content in NbC and the dissolved Nb content increased linearly with Nb content in the coating, when the Nb content of coating and the experimental parameters vary within a certain range. Decreasing the Nb content in the coating can promote NbC phases to change from networks and/or dendrites to particles. The microhardness increases with the content of NbC and dissolved Nb in coating, but the morphology of NbC has no significant effect on microhardness of coating. (C) 2016 Elsevier Inc. All rights reserved.