Due to the poor fracture toughness of hard alloy tool materials, it is difficult to be applied to some machining occasions (such as micro deep hole drilling, etc.) that require high toughness of tools.  An effective way to solve this problem is to use whisker toughening and reinforcing technology.

Whiskers added to hard alloy materials can absorb the energy of crack propagation, and the amount of energy absorbed is determined by the bonding state of whiskers and matrix.

The toughening mechanism of whiskers is mainly shown as follows:

① Whisker extraction toughening: When the whisker is extracted from the matrix under the action of external load, some external load energy is consumed due to interface friction, thus achieving the toughening purpose. Its toughening effect is affected by the sliding resistance between the whisker and the interface.  There must be sufficient bonding force between whisker and matrix interface to effectively transfer external load to whisker, but the bonding force cannot be too large to maintain sufficient pull-out length.

(2) Crack deflection toughening: When the crack tip encounters the second phase whose elastic modulus is greater than that of the matrix, the crack will deviate from the original advancing direction and propagate along the interface of the two phases or in the matrix.  Since the non-planar fracture of the crack has a larger fracture surface than the planar fracture, it can absorb more external energy and thus play a toughening role.  Adding whiskers or particles with high elastic modulus into matrix can cause crack deflection toughening mechanism.

(3) Whisker bridging toughening: When the matrix is broken, the whisker can bear external load and act as a bridge connection between the broken crack surfaces.  Bridged whiskers can generate a force to close the cracks on the matrix and consume external loads to do work, thus improving the toughness of the material.