Abstract: A layer of AlTiCrN coating was prepared on the YT14 hard alloy cutter surface by cathodic arc ion plating(CAIP) with Ti,Al and Cr targets. The morphologies,chemical elements and phases of the coating surface and interface were observed by means of scanning electron microscopy(SEM),energy dispersive spectrometer(EDS) and X-ray diffraction(XRD),respectively. The diffusion mechanism of chemical elements at the interface was analyzed by line scan and plane scan. The bonding strength of the interface was characterized by scratch test,and the binding mechanism was discussed. The results show that phases in the coating mainly are composed of AlN,CrN and TiN,and the crystal plane of(111) has a strong preferred orientation. The concentrations of Al,Ti,Cr and N in the coating are higher than those in the substrate,showing a step-like distribution at the interface. C atoms in the substrate diffuse into the TiN,AlN and CrN lattices to form an obvious diffusion layer. The interface is a mechanical and diffusion form,mainly combined with adsorption bonding,diffusion bonding and chemical combination. The coating bears three stages in scratch process,i. e.,elastic deformation,plastic deformation and coating stripping,and the interface bonding strength is 59.2 N.