Research Some Questions Of High Temperature Infrared Radiant Coating During The Application

As a kind of coating materials for saving energy, high temperature infrared radiant coating can be applied to various industrial furnaces, the coating can enhance the absorptivity and emissivity of thermal radiation, which makes furnace wall absorb and motivate the infrared radiation to heat the furnace cavity in time, or the coating can enhance the absorptivity of thermal radiation and the thermal conductivity, which makes furnace surface absorb efficiently and transfers the energy to heat water, so that the thermal efficiency will be improved. At the same time, because of the strengthening of heat transfer by radiation in the furnace cavity, the temperature uniformity in the furnace can be improved which can improve the heating quality. In addition, the coating has good resistance of anti-oxidation at high temperature to the materials of furnace lining, which can prolong the service life of the industrial furnace and reduce maintenance work.The previous studies in the high temperature infrared radiant coating mainly focused on the emissivity of the coating, that is, the components of the coating for the impact of the emissivity, especially for the components that have high emissivity, such as transition metal oxides, carbide for the impact of the emissivity that is important to improve the effect of saving energy. But on the other hand, the application of the high temperature infrared radiant coating shows that the stability of the coating is the critical indicator, which is not only go wrong easily in the application but also hard to solve. The concrete phenomena of the bond strength and the durability of the coating includes:coating crack, exfoliation, blistering, the erosion by penetrating to the substrate and the coating's color fades away and the loss of coating quality at high temperature for a long time.In allusion to the phenomena of the stability of the coating, we use high aluminum refractory material as substrate. This study researched the effects of Fe2O3, MnO2, CuO and other oxides to the defects at1400℃. Analyses show that: the thermal stress formed during the heating process for the differences of coefficient of thermal expansion between the coating and the substrate; and the volume effect caused by the crystal transfer when the temperature changed result in the coating crack and exfoliation; the gas produced by the reactions between NiO, MnO2act other alkaline or amphoteric oxides and binder during the heating process causes the coating blistering, SiC can't form SiO2protective film, so it produces volatile gases, SiO and CO, during the heating process which also causes the coating blistering; the analyses of EMPA show that oxides with low melting point cause the erosion by penetrating to the substrate, especially Cu and Mn which have lots of thermal defects and deep penetration; the valent changes of Fe2O3and MnO2during the heating process cause the coating's color fades away and the loss of coating quality at high temperature for a long time.