The wear failure mechanism of bucket tooth is related to material and working conditions, mainly including micro-cutting, fatigue spalling and other mechanisms. Generally speaking, micro-cutting wear mechanism plays a dominant role in the wear process of bucket tooth, up to 70%. With the increase of the hardness of bucket toot, the fatigue spalling mechanism increases gradually, accounting for 20-30%. When the material hardness reaches the upper limit, brittleness increases and brittle fracture may occur. In the case of micro-cutting wear mechanism, improving the hardness of the bucket tooth material is beneficial to improving 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 beneficial to improving the wear resistance of the material.

I. Micro-cutting mechanism

When bucket  tooth interact with rocks under high impact load, on the one hand, they contact with the surface of rocks (ores) and produce greater impact force. If the yield strength of bucket tooth is low, plastic deformation will occur at the tip of bucket tooth, thus forming plastic plough grooves. On the other hand, when the bucket tooth are inserted into the rock if the bucket tooth hardness is lower than the rock hardness, the rock particles are pushed into the bucket tooth surface, which will produce long curved or spiral chips, forming cutting grooves, and may be accompanied by micro-cutting debris. Chips are deformed by shearing, resulting in a large amount of latent heat of deformation, compact and orderly sliding steps and wrinkles. In addition, the friction heat between chips and rocks produces friction heat. The combined effect of latent heat of deformation and friction heat makes chips temperature rise sharply, dynamic recrystallization, tempering softening and dynamic phase transformation occur, which changes the internal structure of chips. Some of them also have partial melting.

2. Fatigue spalling mechanism

The bucket tooth insert into the rock for reciprocating motion. The plastic plough formed on the surface of the bucket tooth can be rolled by rock particles for many times to form a metal multi-flow platform. When the stress on the bucket tooth exceeds the strength limit, cracks and brittle cracks will occur and become debris. The debris is split perpendicular to the direction of wear and tear off along the direction of wear. The front of the debris is smooth groove stripe, the back is flat, and the side is overlapping stripe formed by rolling deformation. If the rock has edges and corners, it will shear the deformed layer and form debris, which is flat and thin, with rough edges. In another case, when the bucket tooth interact with rock repeatedly, the bucket tooth produce plastic deformation and cause high work hardening, which increases the brittleness of the bucket tooth surface. Under the strong impact of rock, the bucket tooth surface will form brittle fragments, and the surface of the bucket tooth will have radial cracks of different depths. Strictly speaking, this brittle crack feature is also the mechanism of fatigue spalling.