1. Cutting mechanism
When the bucket tooth acts with the rock (ore) under high impact load, on the one hand, it contacts the surface of the rock (ore) and produces a large impact force. If the yield strength of the bucket tooth material is low, a certain plastic deformation will occur at the tip of the bucket tooth, which is easy to form a plastic furrow. On the other hand, when the bucket tooth is inserted into the rock (ore), if the hardness of the bucket tooth is lower than that of the rock (ore), the rock (ore) particles will be pushed into the bucket tooth surface, which will produce long curved or spiral chips to form cutting grooves, and may be accompanied by micro cutting chips. The chip deforms a lot due to shear action, resulting in a large amount of deformation latent heat, and closely and neatly arranged sliding steps form wrinkles. In addition, its friction with rock (ore) generates friction heat. The combined action of deformation latent heat and friction heat makes the chip temperature rise sharply, dynamic recrystallization, tempering softening, dynamic phase transformation, etc., which changes the internal structure of the chip, and some also appear local melting.
2. Fatigue spalling mechanism
The bucket tooth is inserted into the rock (ore) for reciprocating motion. The plastic furrow formed on its surface can be rolled by the rock particles for many times to form a metal multiple flow table. When the stress of the bucket tooth material exceeds the strength limit, it will produce cracks and brittle cracks into debris. The debris is split perpendicular to the wear direction, and split or torn down along the wear direction. Its front is smooth groove stripes, its back is flat, and its side is overlapping stripes formed by rolling deformation. If the rock has edges and corners, it will shear the deformation layer to form debris, which is flat and thin, and the edge is rough. In another case, when the bucket tooth acts repeatedly with the rock, the bucket tooth will produce plastic deformation and cause high work hardening, which will increase the brittleness of the bucket tooth surface. Under the strong impact of the rock, the bucket tooth surface will form brittle debris with radial cracks of different depths on its surface. This embrittlement feature is strictly speaking also a fatigue spalling mechanism.
The wear failure mechanism is related to the material and working conditions, mainly including cutting, fatigue spalling and so on. Generally speaking, the cutting mechanism plays a dominant role in the wear failure process of bucket teeth, which is more than 70%; With the increase of bucket tooth hardness, the fatigue spalling mechanism increases gradually, accounting for 20% ~ 30%; When the hardness of the material reaches the upper limit, the brittleness increases and brittle fragmentation may occur. For the working conditions dominated by cutting mechanism, improving the hardness of bucket tooth material is conducive to improve its wear resistance; For the fatigue spalling mechanism, the material is required to have a good combination of hardness and toughness; High hardness, high fracture toughness, low crack growth rate and high impact fatigue resistance are conducive to improve the wear resistance of the material.