Preparation Process And Experimental Research Of Thermal Barrier Coating On The Roller Surface Of Liquid-core Heavy Reduction Mill

Liquid-core heavy reduction rolling process has been applied more and more in thethick-plate production, which is the industrial base of a country, because of the importantrole in thinning casting blank and improving the internal quality of slab. However, the rollwhose quality and life has a close relationship with casting quality and productionefficiency scraps easily under the multiple bad working conditions such as hightemperature, low speed and overload. The service life of roll in extreme conditions mustbe improved in order to meet the requirement of practical production.Thermal barrier coatings (TBCs) have been widely used for the protection of varioushot-end sections of the aerospace field, which can be attributed to its low thermalconductivity and excellent chemical stability, extending the service life of hightemperature hot-end components effectively. In this paper, two kinds of thermal barriercoatings were prepared on the surface of H13substrate by plasma spraying and "plasmaspraying+laser remelting" composite technology and were applied to improve the worklife of roll innovatively.The elastic-plastic finite element model of the roll was established by using theABAQUS finite element analysis software. The variation trend of temperature, stress andstrain of conventional roll and thermal barrier coatings roll was compared. The feasibilitythat thermal barrier coatings can reduce the temperature and thermal stress of the roll andextend the service life of the roll was verified.The process parameters of plasma spraying and laser remelting were optimized byexperiments, through which plasma spraying and laser remelting samples were prepared.The microstructures of specimens were observed by SEM, EDS and XRD, whoseinfluence on the performance of coatings was also discussed.The microhardness and adhesive strength of the specimens were examined by fullyautomatic microhardness measurement system and tensile testing machine. The resultsshowed that the inherent defects of the plasma spraying can be improved effectively bylaser remelting technology, resulting in the formation of metallurgical combination. The microhardness and adhesive strength of the laser remelting coating were considerablybetter than the plasma spraying one.The thermal shock and high temperature oxidation experiments were designed inorder to record the morphology and the number of circulation of the coatings after thermalshock and plot the curve of oxidation weight gain. The failure mechanism of thermalshock and high temperature oxidation of the plasma spraying and laser remelting coatingswere discussesed. The results released that the thermal shock resistance and hightemperature oxidation resistance of plasma spraying thermal barrier coatings wereimproved obviously by laser remelting. The composite technology of "plasmaspraying+laser remelting" could improve the coating performance effectively, which wasrecognized as a more promising one for the improvement of the service lifetime of liquidcore heavy reduction mill rolls.