Preparation of cBN@TiN Powder Based on Mechanical Dry Particle Coating Technology
cBN@TiO2(cubic boron nitride coated with TiO2)powder and cBN@(TiO2+C)(cubic boron nitride coated with TiO2+C)powder were prepared by mechanical dry particle coating technology,and then were heated to synthesize cBN@TiN(cubic boron nitride coated with TiN)powder under condition of 1 600 ℃ and N2 atmosphere.The phase composition and microstructure of the powders before and after high temperature heat treatment,as well as the reaction mechanism at high temperature were studied.The results show that the surface of cBN particles could be evenly coated with nano TiO2 and nano TiO2+C particles by mechanical dry particle coating technology.During high temperature heat treatment,the liquid phase B2 O3 generated by the reaction between TiO2 and cBN promoted the phase transformation of cBN into hexagonal boron nitride(hBN),indicating the poor high temperature stability of cBN.A lamellar structure layer composed of TiN phase and hBN phase was formed on the surface of cBN@TiN powder particles prepared with cBN@TiO2 as raw materials.After adding carbon,TiO2 preferentially reacted with carbon to form TiN during heat treatment,which inhibited the generation of B2O3,and thus reduced the phase transformation content of cBN,indicating the good high temperature stability of cBN.The surface of cBN@TiN powder particles prepared with cBN@(TiO2+C)as raw materials formed a particle structure layer mainly composed of TiN.
cBN coated with TiN powderhigh temperature heat treatmentmechanical dry particle coating technologythermal stability
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