Cai Liu-Xi, Li Yun, Wang Shun-Sen, He Yao, Li Fang, Liu Ze-Kun
School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an 710049, China.
State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
Materials (Basel). 2020 Dec 30;14(1):123. doi: 10.3390/ma14010123.
In this study, the high temperature erosion mechanisms and damage characteristics of a boronized coating have been systematically studied by employing an improved high-temperature accelerated erosion test bench and impact contact theory analyses. Within the scope of the experimental parameters, the erosion rate of the boronized coating under the same erosion conditions was observed to be only one half to one-twelfth of the erosion rate of the substrate. Furthermore, the boronized coating was noted to be less sensitive to the speed of the erosion particles than the plastic substrate, thus, indicating superior and more stable erosion resistance than the base material. The boronized coating exhibited typical brittle fracture characteristics under impact by the high-speed particles. When the particle impact normal stress exceeded the critical stress for crack propagation owing to the coating defects, the surface and subsurface layers of the coating initially formed horizontal and vertical micro-cracks, followed by their gradual expansion and intersection. After destabilization, the brittle coating material was peeled layer-by-layer from the surface of the test piece. At the same incident speed, as the particle size was increased from 65 μm to 226 μm and 336 μm, the size (width) of the erosion cracks on the coating surface increased from 1 μm to 30 μm and 100 μm respectively. Correspondingly, the erosion damage thickness of the coating was enhanced from 15 μm to 50 μm and 100 μm. In the case of the quartz sand particle size exceeding 300 μm, the dual-phase boronized coating did not provide effective protection to the substrate. Furthermore, based on the elastoplastic fracture theory, a prediction model for the erosion weight loss of the boronized coatings within the effective thickness range has been proposed in this study.
在本研究中，通过采用改进的高温加速侵蚀试验台并进行冲击接触理论分析，系统地研究了硼化涂层的高温侵蚀机制和损伤特性。在实验参数范围内，观察到在相同侵蚀条件下硼化涂层的侵蚀速率仅为基体侵蚀速率的二分之一至十二分之一。此外，与塑料基体相比，硼化涂层对侵蚀颗粒速度的敏感度较低，因此表明其具有比基体材料更优异且更稳定的抗侵蚀性。硼化涂层在高速颗粒冲击下呈现出典型的脆性断裂特征。当颗粒冲击法向应力由于涂层缺陷超过裂纹扩展的临界应力时，涂层的表面和次表面层最初形成水平和垂直的微裂纹，随后这些裂纹逐渐扩展并相交。失稳后，脆性涂层材料从试件表面逐层剥落。在相同入射速度下，随着颗粒尺寸从65μm增加到226μm和336μm，涂层表面侵蚀裂纹的尺寸（宽度）分别从1μm增加到30μm和100μm。相应地，涂层的侵蚀损伤厚度从15μm增加到50μm和100μm。当石英砂颗粒尺寸超过300μm时，双相硼化涂层无法为基体提供有效保护。此外，基于弹塑性断裂理论，本研究提出了有效厚度范围内硼化涂层侵蚀失重的预测模型。
