Characterization and properties of MTCVD TiCN and MTCVD ZrCN coatings

Medium temperature chemical vapor deposition (MTCVD) coatings, on cemented carbide cutting tools, have gained prominence in the machining of gray and nodular cast iron, stainless steels and other abrasive workpiece materials, that require increased edge toughness of the cutting tools. Although MTCVD TiCN is the most common coating layer used in the current popular cutting tools, other coatings like MTCVD ZrCN used in conjunction can offer potential performance improvements in machining. Properties of mono- and nanolayer hard coatings of TiCN and ZrCN, deposited on carbide substrates by MTCVD, are discussed in this paper. Evaluations of the texture of coatings, along with interfacial features of these hard coatings, are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical microscopy. Surface smoothness/surface roughness was determined on as-coated inserts and compared with physical vapor deposition (PVD) and conventional chemical vapor deposition (CVD) coated tools. Failure mechanism modes of these various coating designs, in machining of nodular iron and 4340 steels, are discussed for delineating the wear properties of the coatings. (C) 1999 Elsevier Science S.A. All rights reserved.