Causes of flank wear are examined first. As a result of examination, it is realized that the elongation of duration untill cBN particles fall off from ceramics binder is effective to improve the wear resistance. By way of extending the duration time, TiN film is coated on surface of cBN particles (size 1-3 μm) by thermal CVD, and cBN tools consisting of TiN coated cBN particles and ceramics binder are fabricated by high pressure sintering process. Using the cBN tools, cutting test of hardened steel is carried out. Main findings are as follows ; (1) The pores appeared in the layer of cBN particles and ceramics binder in cBN compacts made of TiN coated cBN particles show a decrease of number by 1/10, and, its critical stress intensity factor (KIC) shows an increase of 40%. (2) Comparing the cBN tools made of TiN coated cBN particles with no coated one, it is realized that the wear resistance shows an increase of its value by 2 times, and tool fracture resistance is also improved.
