Residual stress in polycrystalline diamond/Ti6Al4V systems

• Published in: Diamond and related materials 1997-04, Vol.6 (5), p.807-811
• Main Authors: Scardi, Paolo, Leoni, Matteo, Cappuccio, Giorgio, Sessa, Vito, Terranova, Maria Letizia
• Format: Article
• Language: English
• Subjects: CVD; Diamond films; Interface/interfacial; Residual stress; Strain; Synchrotron radiation; Texture; Ti6Al4V; X-ray diffraction
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/S0925-9635(96)00605-X

Polycrystalline diamond coatings were deposited on Ti6Al4V alloy by HF-CVD, at fixed temperature (650 C) for different deposition times. During the process, thick titanium carbide layers were formed at the metal/diamond interface. X-ray diffraction (XRD) methods were used to assess coating quality, phase composition, texture, and residual macrostress of the diamond/TiC/Ti system. For a better evaluation of the residual stress present in each phase, three independent measurements were performed with synchrotron radiation (SR-XRD). The measured residual strain could be interpreted in terms of a simple axially uniform residual stress model: σ 11 = σ 22, σ 33 = 0, σ ij = 0 ( i ≠ j). Irrespective of film thickness, the residual stress was very intense, compressive both in the diamond layer (approx. −6.5 GPa) and in TiC (approx. −1.4 GPa), and tensile in Ti6Al4V (approx. 70 MPa). The high residual strain in the diamond layer affected the results of texture measurements using the traditional pole figure method; more reliable results were obtained by measuring the integrated intensity, rather than peak maximum intensity, as a function of tilting angles.