Powder metallurgy parts require only a small amount of processing, but machining powder metallurgy parts is extremely difficult, especially for the cbn inserts, mainly due to the porous 

structure of the powder metallurgy material. And this porous structure will result in:

(1) The cutting edge is not wear resistant;

(2) The cutting edge temperature is high, causing inserts wear and deformation;

(3) The intrinsic porous structure causes an increase in surface area, which causes oxidation or carbonization during heat treatment, and these oxides and carbides are very hard and 

wear-resistant;

(4) Due to the presence of voids, the hardness values also fluctuate within a small area. Although the measured macro hardness is HRC20-35, the hardness of the particles of the 

components will be as high as HRC60, and these hard particles will cause serious and sharp edge wear;

(5) Many powder metallurgy parts are harder and have higher strength after heat treatment;

(6) There may be impurities in the parts. These problems are all called the problem of difficult processing of powder metallurgy parts.