Analysis on Oxidation and Wear

 The hardness of cubic boron nitride is second only to diamond, and these two abrasives are usually called superabrasives. Because of their superior mechanical wear properties, chemical wear is particularly important, and its laws should be mastered.

         When the temperature is lower than 2000°C, cubic boron nitride is stable, and it will transform into hexagonal boron nitride at 2500°C, and the hardness will decrease. At high temperatures, the surfaces of the grains oxidize and transform into glassy boron oxide. Due to the presence of nitrogen in the atmosphere, this oxidation process is a locally reversible reaction. In comparison, the thermal stability of cubic boron nitride is much better than that of diamond. Under normal grinding conditions, the temperature at the cutting point of abrasive grains is not As for exceeding its thermal stability limit temperature (2000°C) (generally, the highest temperature at the grinding point is approximately the melting temperature of the ground material). However, in water vapor, when the temperature exceeds 1000 ° C, cubic boron nitride will undergo hydrolysis. When it reaches 1200 ° C, the luster of the grain surface will disappear, and cracks and corrosion spots will appear. Its reaction is:

                BN+3H2O→H3BO3+NH3

         Tests have shown that water vapor has a catalytic effect on cubic boron nitride, which will accelerate its wear. Therefore, this abrasive is suitable for grinding or oil-based grinding fluid. Both diamond and cubic boron nitride have high hardness and are sharper than ordinary abrasives. Therefore, the temperature of CBN abrasives is lower than that of ordinary abrasives, which is beneficial to reduce oxidation wear.