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所谓镀层“牢固喷着”在基材上,指的是粉粒喷着瞬间,在喷着点范围里大约有60%的基材表面原子被活化而进入键合。这时,两相之间的粘结呈现出“点钎焊”或“烧结”结构的特征。这种结构只有在喷着点温度升至相当高时才可能形成。利用喷着活化能略低于扩散活化能的假定,可以算出任一基材的喷着点温度。所需的喷着点温度要依靠喷着瞬间粉粒对基材的传热来获得。利用描述喷着瞬间、喷着点微区中的传热过程的物理模型就可以对不同的粉料算出所需的粉料加热温度。这个温度反映了该种粉料在给定的基材上达成牢固喷着的难易程度,所以可用作选择打底层材料的理论准则。我们用上述方法,对紫铜和黄铜基材上的热喷镀作了理论预测,并进行了相应的实验验证。
The so-called coating “firmly spray” on the substrate, refers to the instant powder particles sprayed in the spray point range of about 60% of the substrate surface atoms are activated into the bond. At this point, the bonding between the two phases exhibits the characteristic of “spot-brazed” or “sintered” structures. This structure can only be formed when the temperature at the injection point rises quite high. Using the assumption that the activation energy of the sputter is slightly lower than the activation energy of diffusion, the spray point temperature of either substrate can be calculated. The required jetting temperature depends on the instantaneous heat transfer of the particles to the substrate. Using a physical model that describes the heat transfer during a spray, the desired powder heating temperature can be calculated for different powders. This temperature reflects the ease with which the powder is firmly sprayed on a given substrate and is therefore used as a theoretical guideline for selecting primer materials. We use the above method, the copper and brass substrate thermal spraying theory made a prediction, and the corresponding experimental verification.