Mechanism of cracks generation in hardfacing pinch roll

Hot cracks formed in pinch roll frequently after repaired by hardfacing because the material was chosen improperly and low purity. This happened even if the hardfacing technique and the heat treatment are suitable. After repairing the simulated pinch roll by hardfacing, hot cracks were found and analyzed by optical microscope and scanning electron microscope. The results show that the net cracks composed of main cracks and micro cracks near the main cracks. High content of carbon, sulfur and oxygen were detected in the main cracks. A lot of low-melting eutectics formed because of these elements interaction. Meanwhile these impurities concentrated on the grain boundary or between dendrites, so that the solidification cracks formed and extended. A great number of oxides existed in micro cracks and their segregation and aggregation resulted in micro cracks.