Theof the edw-300-l drum shearer is 17crnim06e steel. The heat treatment process is quenching and tempering, and it breaks during operation. The macro fracture morphology of gear teeth is shown in Figure 17, with the macro characteristics of fatigue fracture, and the electron micrograph is shown in Figure 18.
Based on the above analysis, it can be seen that the fracture of 17crnim06e steel gear teeth belongs to unidirectional bending low cycle fatigue fracture, and the fracture source area basically presents the morphology of intergranular and transgranular quasi cleavage fracture; with the growth of the crack, the fatigue growth rate gradually increases, that is, the fatigue striation increases. The instantaneous fracture zone is a quasi cleavage feature.
The single tooth bending low cycle fatigue crack is inclined to the gear slot. The crack of gear tooth is initiated and propagated from the root of working face, and the direction of crack propagation is from working face to non working face. The direction of crack propagation changes continuously, and finally reaches the non working face to form fracture. The fracture surface of gear teeth is relatively flat, which may be caused by hardening layer. The crack of gear tooth is fanned to the interior.
Gear tooth fracture of shearer. The electronic image of the crack source region is characterized by the intergranular brittle fracture morphology.