טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentGreenman Gadi
SubjectMicrostructure and Properties of TiCN CVD Coatings
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Wayne D. Kaplan
Full Thesis textFull thesis text - English Version


Abstract

Medium temperature chemical vapor deposition (MTCVD) coatings on cemented carbide cutting tools have gained prominence in the machining of gray and nodular cast iron, steels, and other abrasive materials, that require increased edge toughness and wear resistance of the cutting tools. MTCVD TiCN is the most common coating layer used for conventional cutting tools.

 TiCN coatings produced by MTCVD were investigated.  The influence of CVD deposition variables such as temperature, pressure and H2 flow on the preferred orientation, grain size, surface morphology, deposition rate, surface roughness, hardness and thermal stability was investigated.  The preferred orientation of the TiCN MT was characterized using X-ray diffraction (XRD). Scanning electron microscopy (SEM) and optical microscopy was used to characterize the morphology of the coating.

The deposited TiCN MT coatings had a twinned columnar microstructure with a preferred orientation that depends on deposition conditions. The results indicated that the deposition temperature is a critical factor that can be effectively used to control the morphology and structure of the coating. High temperature deposition results in the formation of a {220} preferred orientation. Low temperature deposition conditions results in {311} and {422} preferred orientation.

Control of the microstructure provides a method to optimize the mechanical properties for a specific cutting application. For example, TiCN MT coatings deposited at 750oC tend to be more stable during interrupted cutting conditions because of low hardness. On the other hand, higher temperature deposition (975oC) resulted in improved results for continuous cutting because of high hardness and thermal stability.