Damage of heat-resistant castings in a carburizing furnace

The study reviews typical damages occurring in heat-resistant castings used in box-type carburizing furnaces. The analysis was mainly based on a visual examination of elements withdrawn from operation. Furnace heat-resistant equipment can be divided into construction elements installed permanently in a furnace chamber (e.g. radiant tubs, fans, rollers) and elements utilized to set or load and unload parts to be carburized (e.g. grates, fixtures, basket). Depending on the function performed by a particular casting, its degradation process varies. The final consequence of the wear and tear of a casting is above all a decohesion of its walls that results from an influence of carburizing atmosphere, or from the combined effect of carburizing atmosphere and thermal fatigue. The effect of creep, that may occur in castings during their use as a result of the load of the structure or/and of the carburized parts, was not observed to be a direct cause of the damages.