The appearance of the PVD coating affects the sales of coated parts, and the bright, complete and beautiful coating appearance gives a good visual impression. The apparent defects in the functional area affect not only the appearance of the coating, but also the service life of the coating. The apparent defects of the coating are mainly flaking and color difference.
This is determined by the characteristics of the coating process. The old coating deposited on the furnace walls and fixtures during the previous coating process will continue to crack and some fragments will cling to the workpiece. The new coating covers these fragments instead of the substrate. In this way, the old coating falls off together with the new coating during the cooling or subsequent process. The severity of coating flaking is related to the location and size of the shedding point. And the coating shedding can be inspected by microscopic magnifiers.
◆ Color Difference
Chromatic aberration refers to the difference in the color of the same coating. There are mainly two situations: one is the color difference of the workpiece in different positions in the same furnace, and the other is the color difference of different furnaces. The color difference is related to the substrate material, the distribution of the reaction gas in the furnace, the weight of the target, and the different vacuum degree. Under normal circumstances, slight color difference does not affect the performance of the coating. The composition analysis instrument can be used to analyze the difference between coating compositions of different colors, and also the severity of the effect of the color difference on the coating performance can be judged. In actual production, slight color difference will not affect the performance of the product, so it doesn’t draw much attention. Big color difference is obvious to naked eye, so we must pay attention to it and find out the reasons.
When inspecting products such as colored stainless steel screens, special attention should be paid to the above two types of apparent defects.