Dependence of phase composition on dry sliding behaviour in nanocomposite TiBxNy thin films

TiB_xN_y thin films with different N contents were deposited using unbalanced magnetron sputtering at room temperature. Their structure, phase composition, hardness and dry sliding behaviour were investigated by X-ray diffraction, X-ray photoelectric microscopy, microindentation, pin on disc and scanning electron microscopy. The results indicated that the phase composition in TiB_xN_y thin films strongly depended on N content. Nanocrystalline (nc-) TiN was preferentially formed with incorporation of N into TiB_0.65 till its mole fraction reached a maximum at ∼37 at.-%N. BN was promoted to be formed with further increasing N content. Both friction coefficient and wear rate strongly depended on phase composition rather than hardness. The friction coefficient was increased with increasing N content till its maximum, accompanying with the least amount of deformed wear debris, was achieved at the mole fraction maximum of nc-TiN. A decrease in friction coefficient was followed after formation of BN, accompanying with increasing amount of deformed wear debris. The wear rate showed an inverse trend. During wear procedure, adhesive and abrasive wears coexisted and wear debris was oxidised to form the debris comprising of various types of Ti and B oxides. © 2007 Institute of Materials, Minerals and Mining.