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本文通过把不同成份的钢试样,在相同的气氛及工艺条件下,进行化学气相沉积后,用光学显微镜及扫描电子显微镜观察并分析不同沉积时间下得到的试样的显微组织变化。根据化学气相沉积理论,提出了在不同含碳量的普通碳铜的基体上覆层的形成机制。并且应用这一机制使实验结果得到了令人满意的解释。采用了倾斜剖面试样,恰当的试样制备方法,并选用了合适的浸蚀剂,成功地显示了 TiC 覆层与基体之间过渡层组织。并根据过渡层中各元素的分布,弄清了过渡层的形成原因。为作者在以前工作中提出的“予先进行 CN 共渗处理,再进行化学气相沉积,可以使覆层与基体间的结合力有所提高,其原因是因为过渡区中存在 TiN,因而减少了 TiC 层与基体间的热膨胀系数之差。这一说法找到了实验根据据。经过 TiC 化学气相沉积的试样,在静载荷和冲击载荷作用下,使覆层开裂并剥落。然后对裂纹的宏观形貌进行观察。提出了在静弯曲条件下覆层中裂纹的萌生,扩展及剥落的规律。
In this paper, the chemical composition of the steel samples with different composition under the same atmosphere and process conditions was observed by optical microscope and scanning electron microscope. The microstructure changes of the samples were observed under different deposition time. According to the theory of chemical vapor deposition, the formation mechanism of the coating on the substrate of ordinary carbon and copper with different carbon content is proposed. And the application of this mechanism has made the experimental results satisfactorily explained. Tilt profile specimens, proper specimen preparation methods, and the use of a suitable etchant have been used successfully to demonstrate the microstructure of the transition layer between the TiC cladding and the substrate. According to the distribution of the elements in the transitional layer, the reasons for the transitional layer were clarified. For the author in his previous work proposed "CN advance osmosis treatment, followed by chemical vapor deposition, can make the bonding between the coating and the substrate increased, the reason is because there is transition zone TiN, thus reducing the TiC layer and the difference between the thermal expansion coefficient of the substrate.This argument found the experimental basis.After TiC chemical vapor deposition of the sample, under static and impact loads, the coating cracking and exfoliation.And then the crack macro The morphology was observed, and the law of initiation, propagation and spalling of cracks in the coating under static bending condition was proposed.