| Tungsten-Rhenium?W-Re?alloy thermocouple is one of most commonly used high temperature sensors whose measuring upper limit could achieve to 2800 ?.However,W-Re alloy is very easy oxidized at high temperature.It should be used in reducing,inert and vacuum atmosphere.While it used in oxidization or air atmosphere,anti?oxidization protection should be applied.The purpose of this research is to fabricate oxidation resistant coatings?ORCs?and develop a proper coating process of ORCs.ORCs should improve the upper limit of measuring temperature and working time in oxidization atmosphere on the basis of no extended of reponse time of thermocouple.Based on the research of the high temperature oxidation resistant coating and functional gradient films' excellent performance,ZrO2 is selected as an oxidation resistant coating material and ZrO2+Zr gradient thin films are designed as an anti-oxidation coating.ZrN thin films is deposited between ZrO2+Zr gradient thin films and W-Re Alloy thermocouple wire,because the coefficient of linear expansion of ZrN is between them.The results of a study of the ZrO2+Zr thin films deposition process and the technological development of cathodic arc are presented there.The ZrO2 film prepared by different technological parameters has a metal Zr,that is,the composition of the film is ZrOx?x is between 0-2?.In this paper,by changing the Pre heating temperature,substrate negative pressure and oxygen partial pressure and other technological parameters,the preparation of ZrO2+Zr film is studied.Some conclusions were drawn by the method of electrical conductivity detection,SEM and XRD.The substrate negative bias has a effect on the crystal structure of the film when 160V?80V.With the increase of oxygen partial pressure,the ratio of O:Zr in the films increased,and the maximum reached 1.853:1.ZrO2-Zr gradient thin films are produced on W-Re Alloy Thermocouple.On the production process,by changing the oxygen pressure,the gradient films on composition and structure are obtained in the radial direction;through flipping the thermocouple wire,the film uniformity are obtained in the circumferential direction.Finally,in the oxyacetylene flame tested 1900? oxidation atmosphere.Tungsten-rhenium thermocouples can stay 7 minutes under the temperature of oxidation,oxidation coating does not fall off. |
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