Intrinsic Stress and High Temperature Properties of Metal-Containing Hydrogenated Amorphous Carbon Coatings

• Main Author: Shi, Bo
• Other Authors: Kevin W Kelly
• Format: Others
• Language: en
• Published: LSU 2005
• Subjects: Mechanical Engineering
• Online Access: http://etd.lsu.edu/docs/available/etd-04202005-161203/

A detailed examination of the intrinsic stress development and mechanical properties of titanium-containing hydrogenated amorphous carbon (Ti-C:H) and W-C:H coatings, deposited in an inductively coupled plasma (ICP) assisted hybrid chemical/physical vapor deposition (CVD/PVD) environment was carried out. Intrinsic stresses within those coatings were found to be compressive and dependent on compositions. The intrinsic compression within Ti-C:H was further shown to be significantly influenced by the energy of ionic species bombarding the substrate during growth. The results suggested that ion bombardment played a significant role in intrinsic stress generation within Ti-C:H, and was likely to influence stress development in other low temperature deposited amorphous hydrocarbon (a-C:H) based ceramic nanocomposite coatings. A higher deposition temperature, ~600C, promoted TiC precipitation and resulted in little Ti dissolution within the a-C:H matrix. High-temperature deposited Ti-C:H specimens were found to possess lower modulus and hardness values as compared to those deposited at low temperature, ~250C, especially at low Ti compositions. This is rationalized by electron microscopy evidence of increased short and medium range graphitic order within the a-C:H matrix of high-temperature deposited Ti-C:H, and supported by additional Raman spectroscopic observations. Annealing treatment at 600C combined with Raman scattering measurements showed that the a-C:H matrix in high temperature deposited Ti-C:H specimens appears to be less structurally sensitive to additional high temperature annealing. The effective coefficients of thermal expansion (CTE) of Ti-C:H coatings were measured through temperature induced changes in the curvature of film/substrate assemblies. Measured effective CTE values for Ti-C:H are consistent with previous measurements on a-C:H thin films, and show little dependence on the Ti composition. Highly hydrogenated carbon coatings with hydrogen content approaching 60 atomic percent were deposited with a modified ICP-assisted CVD technique. The hydrogen release temperature was found to be above 500C, which was 150C higher than findings in previous experiments. Plasma diagnostics suggested that a decreased ratio of ionic species flux to activated neutral species flux at the substrate during deposition was responsible for the increased hydrogen incorporation into the film.