High Temperature Oxidation Resistant Coatings Of W-Re Alloy Thermocouple By Electron Beam Physical Vapor Deposition

With the rapid development of science and technology and increasing needs of measuring ultra high temperature environment,which puts forward a new challenge to the research career of thermocouple in China.However.W-Re alloy thermocouples,as measuring ultra high-temperature thermocouples.only could use in the absence of oxidation atmosphere.which greatly limit those applications.High temperature Oxidation resistant coatings of W-Re alloy thermocouple is urgently needed.A W-Re alloy thermocouple,studied in this paper,should be under the environment of higher than 2500 degrees of liquid steel temperature.According to the melting point of common high temperature materials,anti-oxidation ability and the price,this paper choose zirconia as a high-temperature anti-oxidation material of W-Re alloy thermocouple.And according to the properties of zirconia coating materials and the existing coating preparation method,this paper selects the electron beam physical vapor deposition as a way to deposit zirconia coating on a W-Re alloy thermocouple.Due to W-Re alloy thermocouple wire and the thermal expansion coefficient of zirconia ceramics vary too much and bonding strength is bad,so they need a transition layer.And the choice of transition layer is not only affecting the role of high temperature anti-oxidation of thermocouple,but also its thermal expansion coefficient must between metal matrix and ceramic coatings which makes both has good bonding strength.Ultimately,this paper determines to use the mixture of zirconium and zirconium nitride as the transition layer material and select filtering arc ion coating machine as deposition device.The life of an prepared W-Re alloy thermocouple,which provides higher than 2500 degrees of oxyacetylene flame,are four minutes after oxidation test.And greatly improves the shortcoming of these thermocouples which easily oxidized in high temperature environment and expand the applications.And according to the anti-oxidation test of temperature-time curve.we analyze the anti-oxidation mechanism of anti oxidation coating.Continuing to add the mixture of zirconium and zirconium nitride transition layer,and then through electron beam physical vapor deposition method to the preparation of zirconium oxide coating and in guarantee its performance on the basis of as far as possible to increase its thickness and layers is a way to extend the service life of W-Re alloy thermocouples.