Failure Analysis of Surface Coatings on Furnace Rolls in Annealing Line

Failure reason of the surface coatings on furnace rolls of a company's cold-rolled continuous annealing furnace was analyzed by means of scanning electron microscopy,energy dispersive spectrometer,X-ray diffraction,etc.The results show that the main reason for the furnace roller coatings failure was the concentration of S,Zn and Na elements on the surface of the coating,which reulsted in the growth of “bulge objects” mainly composed of ZnS phase.With the continuous growth and falling off of this kind of “bulge objects”,the quality of the coating had been seriously affected and the final failure of the coating occurred.At the same time,a certain degree of oxidation of the interface between coating and the base metal accelecrated the failure of the coating.