Check whether the vacuum furnace equipment of the pvd coating machine has air leakage: this can be determined by the pressure rise rate index of the vacuum furnace; Here we need to remind everyone that when testing the pressure rise rate, it is necessary to dry the furnace and then cool it to room temperature before testing, instead of opening the furnace door and then vacuuming for testing.

Check whether the air inlet pipe of the vacuum furnace leaks: sometimes we test that the pressure rise rate of the vacuum furnace is normal, but the air inlet pipe or valve of the vacuum furnace leaks. The pressure in the air inlet pipe is gradient, and the closer the furnace body is, the more negative pressure is. This is one of the reasons why the color of the products processed by the vacuum furnace is incorrect.
Detect whether the purity of the inert gas passed into the vacuum furnace is high or not: when the purity of the inert gas is not high enough, the oxygen mixed in the inert gas will lead to oxidation, decarburization and other behaviors of the product, which will lead to discoloration of the product. The purity of the detected gas can be directly detected or compared with other equipment to draw conclusions.
The moisture in the vacuum furnace equipment of the pvd coating machine is attached to the inner wall of the vacuum furnace or the heat exchanger: this kind of moisture is difficult to be discharged through the oven drying method. When the vacuum furnace equipment does not have the above three problems, the color of the processed products is still incorrect, which is mostly caused by this reason; At this time, we can raise the vacuum furnace equipment to a high temperature, stop heating, and then inject high-purity inert gas into the furnace, and then start the fan circulation system to use the high temperature and hot air in the vacuum furnace to bake out the moisture attached to the inner wall of the vacuum furnace and the heat exchanger, so as to solve this problem.
Reasons for quenching oil: In practice, the author found that a large part of the reason why the color of vacuum oil is not bright after quenching is due to improper selection of quenching oil.