| Cr20Ni80 alloy is one of the most important nickel-chromium eletrothermal alloys.It is widely used in electric heating field such as household appliances and industrial heat treatment furnaces.The Cr20Ni80 alloy has stable and excellent comprehensive properties becasuse the microstructure of Cr20Ni80 alloy does not change and keeps Austenite from room temperature to melting point.For example,the electrical resistivity is stable,the alloy has a high melting point,a small thermal expansion coefficient,excellent high temperature oxidation resistance,good high temperature strength and mechanical properties,and no magnetic properties at room temperature.In recent years,the research on electrothermal alloys has been the focus and hotspot of many scholars at home and abroad.At present,China has become a major producer of electric heating alloys,which can produce various grades of electric heating alloys.Moreover,the research level has already reached the level of developing new electric heating alloys,and the electric heating alloy system with Chinese characteristics has been established.However,the quality of Cr20Ni80electrothermal alloy produced in China is still not as good as that of similar foreign products,such as the service life of Cr20Ni80 electrothermal alloy is far shorter than that of imported products.Because the service environment of Cr20Ni80electrothermal alloy is generally in the medium and high temperature environment,the high temperature oxidation resistance has a profound impact on its service life.The high temperature oxidation resistance of the alloy is directly related to the oxidation film formed process and the reason of its failure during service.Therefore,in order to improve the service life of Cr20Ni80 electrothermal alloy,this paper prepared diffusion aluminizing coating on the alloy surface and provided basic theoretical data for the production and processing of electrothermal alloy.In this study,PECVD-12II-3Z/G type vacuum tube furnace was used to prepare diffusion aluminized coating on the surface of Cr20Ni80 electrothermal alloy wire by solid powder embeidding method.The non-alumnized and aluminized Cr20Ni80electrothermal alloy wires were heated by electricity through the high resistance electrothermal alloy accelerated life device at the constant temperature of 1000?,1100?and 1200?.The samples were oxidized by continuous electrification at different times.By means of electron probe micro-analyzer?EPMA?,scanning electron microscope?SEM?,energy dispersive X-ray spectroscopy?EDS?,X-ray diffraction?XRD?and other characterization methods,the surface morphology of aluminized coating,alloy wire and oxide film were studied and analyzed.The oxidation kinetics of different samples was studied by the Mettler Toledo TGA2 tga analyzer.The main findings are as follows:?1?The oxidation kinetics curves of 5 different samples of Cr20Ni80electrothermal alloy wire were basically in line with parabolic law.Among them,the oxidation and weight gain rate of the Al-1%CeO2 sample is the slowest,reaching the level of complete oxidation resistance.Compared with the non-aluminumed sample,the oxidation and weight gain rate is reduced by 43%,effectively protecting the alloy body,and greatly improving the oxidation resistance of the Cr20Ni80 electrothermal alloy wire.?2?The resistance changes with time and accelerated life of Cr20Ni80electrothermal alloy wire were studied for samples without coating and with coating by single aluminized and Al-CeO2?0.5%,1%,2%?.The results show that the oxidation process of the sample can be divided into three stages,namely the formation stage of the oxide film,the stabilization stage of the oxide film and the failure stage of the alloy wire.The accelerated life of the single aluminized sample was increased by 7.62%compared with the non-aluminized sample,while the accelerated life of Al-1%CeO2 sample was increased by 11.81%compared with the single aluminized sample and 20.34%compared with the non-aluminized sample. |
PDF Full Text Request