Observation and analysis of tungsten carbide roll cracking

Observation and analysis of tungsten carbide roll cracking:
There are two types of die cracking: one type of crack originates from a severe abrasion or the sharp corner of the pit due to spalling, as shown in Figure 2-18; The other crack extends from the inner surface of the cavity to the outer surface of the die, penetrating the entire die wall, as shown in Figure 2-19. From the fracture, the penetration crack originates in the upper part of the inner surface of the cavity, near the die opening, expands downwards and penetrates outward.
The microscopic fracture analysis of the crack showed that the fracture had a mixed morphology of quasi-cleavage and dimple. The source of cracks in quasi-cleavage cracking is often intracrystalline pores, non-metallic inclusions, or hard spots, such as carbide particles.

Conclusion of failure analysis of tungsten carbide rolls.
Based on the above observational analysis, the following preliminary conclusions can be drawn:
(1) The main failure modes of Cr12MoV roller cold heading die are radial cracking and cavity surface spalling, which will also cause failure when the surface is seriously bruised.
(2) The spalling of the cavity surface is caused by surface abrasion and impact contact fatigue.
(3) The cracking of the die is the result of the action of periodic impact tangential tensile stress, and the crack originates at the abrasion on the surface of the cavity or the sharp corner of the spalling pit, and gradually expands downward and outward.
(4) Cr12MoV contains a large amount of carbide, which may be an important cause of crack initiation and propagation.
(5) The occurrence of abrasion indicates that the hardness and wear resistance of the inner surface of the mold cavity are insufficient.

Leave a Reply

Your email address will not be published. Required fields are marked *