Briefly Discussing the Effect of Volatilization of Alloying Elements in Deposited NiCrWTi Alloy Coatings

In Russia, this technique was applied in 1988 to deposit NiCrAlY and CoCrAlY thermal barrier bond coats with a coating thickness of 30m-100m. It was used for the coating of aircraft engine blades and turbine blades. In a similar time, vacuum arc was applied. Ion plating deposition of multi-component alloy coating technology, systematically extended, expanded to include W, Zr and other varieties of multi-alloy target material preparation and deposition of the corresponding multi-alloy coating on the metal substrate, and has been steadily moving towards industrialization . The difference is that the research and application of NiCrAlY thermal barrier bond coatings in China has received relatively unanimous attention, while the systematic research and application of multi-alloy coatings other than NiCrAlY is still relatively fragmentary and has not received the expected results of research and application. . As an innovative research work on the deposition of multi-alloy coating materials by vacuum arc ion plating, we developed NiCrWTi multi-element alloy coatings in 1999.

At the deposition temperature of 500600, the vacuum degree is 110-52Pa, the sample is 250mm from the cathode evaporation source, the rotation speed is 20r/min clockwise, the negative bias of the substrate is 01500V, the arc current is 70150A, and GX8 (15Cr12Ni2WMoVNb), W18Cr4V, 1Cr18Ni9Ti NiCrWTi alloy coating is deposited on the substrate, the coating thickness is 0025004mm, 400 alloy coatings are deposited under the same deposition process parameters, and the conventional alloys are subjected to conventional process performance comparison tests to expand the NiCrWTi alloy coating. In the scope of performance tests, vacuum arc ion plating TiN coating and vacuum ion nitriding strengthened layer samples were introduced as reference objects for comparative test study.

Effect of Volatilization of Alloying Elements in Deposited NiCrWTi Alloy Coating During the deposition of NiCrWTi multi-element alloy coating, the content of alloy elements in the alloy target and the content of deposited metal on the surface of the substrate are not constant and the value does not change. Each alloy element has a different boiling point so that all of the alloying elements in the evaporation material do not evaporate at the same time. We know the evaporation boiling points of Ni, Cr, W, Ti alloying elements: Cr 2670, Ni 2912, Ti 3287, W 5662, and multi-alloy film layer components deposited on the substrate and NiCrWTi cathode alloy target alloy. There are some differences in composition. The transfer of the film layer is mainly achieved by metal evaporation. On the surface of the vacuum arc NiCrWTi multi-alloyed alloy, the cathode spot itself easily forms a tiny volume of 3,000 or more high-temperature boiling points on the cathode surface. The higher the boiling temperature, the lower the boiling point of the alloying elements evaporates. The faster and continuously changes. Research shows that the mass loss of metal depends mainly on the evaporation rate of the metal. Compared with Ni, Ti, and W alloying elements, Cr, Ni, Ti, and W exhibit a certain loss, but the Cr loss is more intense. Cr was found to be volatile and there was a large variation in randomness in the test. The content of Cr in the NiCrWTi alloy coating always shows a decrease compared to the content in the target. Therefore, to design the total content of the original chemical composition of the NiCrWTi alloy target, the Cr content should be raised to a certain range, so as to ensure that the content of the alloy coating reaches a desired stable value. Influence of gas pressure on coating thickness When the saturation vapor pressure of Ni, Cr, W, Ti alloying elements is in the range of 10-510-3 Pa (evaporation temperature: Cr is 960, Ti is 1200, Ni is 1200, and W is 2900) If the substrate temperature is set and the gas pressure is changed, the alloy coating of the deposited substrate fluctuates. During the test, vacuum arc ion plating vaporizes Ni, Cr, W, Ti alloys, the deposition time is 120 min, the substrate temperature is 550570, and the negative bias Pressing adopts 200900V, 9001500V bidirectional switching mode. If the vacuum degree (gas pressure) is changed from 110-5Pa to 110-1Pa, as shown in Fig. 5, the coating thickness is reduced from 03mm to 001mm. With the increase of gas pressure, the coating Thickness decreases.

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