The Study Of The Influence Of Cr On The Cyclic Oxidation Life Of Hot-dipped Coating

Hot-dipped aluminized steel possess the property of strong resistance to high-temperature oxidation, erosion and abrasion, thus it has been widely used in the petrochemical, metallurgy, and electric power industry. Alloy element Cr has the physical property of high melting point and low expansion coefficient, and it is one of the most commonly used alloy element in steel family. Yet people have done little research on the effect of element Cr on the property of infiltration layer of hot dipped aluminized steel. To extend the service life of the infiltration layer of aluminized steel in the condition of high temperature, this thesis studies on the 800℃high temperature cycle oxidation of aluminized on Q235 steel and aluminized Cr alloy coatings prepared in 750℃environment and after a time of 4 minutes, and at the same time make a contrast of pure aluminum sample with samples of different Cr content in cycle oxidation weight-gaining and infiltration layer.In this experiment, two-bath method is used to prepare the hot dipped aluminized steel sample. The condition of cycle oxidation is:the sample is put in 800℃environment for 11 hours, and then it is cooled in room temperature for 1 hour. This is an oxidation cycle process. "TIMES TT220" digital magnetism thickness instrument is used to measure the thickness of the infiltration layer, and 4XC series metallographic microscope is used to watch microstructure and then the scan analysis is made. The finding result of cycle oxidation experiment in 800℃temperature indicates that the oxidation weight-gaining of aluminized and aluminized Cr alloy layer present the law of first adding and then losing. This experiment also made the contrast of the pure aluminum sample with samples of different Cr content in infiltration layer hole and crackle, by studying morphs of infiltration layer crack in the process of cycle oxidation, it analyzed the cause of the crack, and then come to the conclusion that the crack is mainly concerned with hole in infiltration layer,loss of Al2O3 film in infiltration layer surface and the difference in coefficient of expansion between alloy layers. It also analyzed the effect of Cr on the infiltration layer crack, and thus indicates that 0.6% Cr content can make the integrative property of hot-dipped infiltration layer best and propose the way to extend the service life of infiltration layer in high temperature, thus indicate the direction of this field in future.