Research On Infrared Spectral Emissivity Characteristics Of Superalloys

Superalloys are widely used in high temperature and high pressure scenarios such as aerospace,petroleum industry,and nuclear power industry due to their good fatigue strength,yield strength,tensile strength,corrosion resistance,and oxidation resistance.Emissivity is an important indicator for evaluating the performance of superalloys,but it is easily affected by various factors such as material composition,temperature,oxidation,and surface roughness.In this thesis,K465,GH3044 and austenitic 304 alloys are taken as the research objects,and based on the energy method and reflection method emissivity measurement devices,the emissivity characteristics of near-infrared band were systematically studied.The main research contents include:（1）According to the research requirements of the emissivity characteristics,the emissivity measurement devices based on the energy method and the reflection method were adopted respectively.The wavelength range of the two sets of devices is 900～2500nm,the temperature range of the energy method measurement device is 550～1150 ℃,and the reflection method measurement device is suitable for emissivity measurement at room temperature.After testing,the linearity of the spectrometer could reach 99%;the repeatability errors of the two sets of emissivity measurement devices were both less than 3%,and the repeatabilities were good.（2）The effects of composition,oxidation and temperature on the emissivity properties of superalloys and the variation of emissivity with wavelength were investigated using the emissivity measurement devices.Superalloys with different compositions,structures and production processes have different emissivity properties.The effect of oxidation on emissivity is mainly reflected in the increase of emissivity and the oscillation phenomenon caused by interference effect.Generally speaking,the emissivity of superalloys will increase with the increase of temperature and decrease with the increase of wavelength,but the difference of measurement environment will lead to the existence of differences.In general,the emissivity characteristics of superalloys are affected by a variety of factors,and the degree of influence of different factors is different under different conditions.（3）Aiming at the effect of roughness on the emissivity characteristics of superalloys,a two-dimensional Gaussian random rough surface model was established and the rough surface was divided into triangles to calculate its surface area.The roughness factor and the functional relationship model between emissivity and roughness were obtained.Using this method,the variation of the emissivity with the root mean square height of the material surface and the wavelength were theoretically studied.Finally,the measured and calculated values of the rough surface emissivity of the three alloys were compared and analyzed through experiments.Except for the changes in the characteristics of some alloys and the errors caused by the low signal-to-noise ratio at short wavelengths,the errors between the calculated values and the measured values were less than 5 %.The spectral emissivity of K465,GH3044 and austenitic 304 alloys and the changing laws of various factors were studied in this thesis.Since the surface morphology of the samples heated under natural conditions changed greatly after the experiment,the influence factor of roughness was mainly studied.The theoretical model of rough surface was established and verified by experiments,and good consistency was obtained.This paper will further enrich the research on the infrared spectral emissivity characteristics of superalloys,and provide theoretical and data support for the application of superalloys in scientific research and industrial production.