Highly adherent tungsten-containing diamond-like carbon (W-DLC) coating on a NiTi shape memory alloy under 10% tensile strain

• Published in: Diamond and related materials 2009-02, Vol.18 (2), p.403-406
• Main Authors: Takeno, Takanori, Shiota, Hiroyuki, Sugawara, Toshifumi, Miki, Hiroyuki, Takagi, Toshiyuki
• Format: Article
• Language: English
• Subjects: Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deposition by sputtering; DLC; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; High adhesive strength; Materials science; Mechanical and acoustical properties; Methods of deposition of films and coatings; film growth and epitaxy; Physical properties of thin films, nonelectronic; Physics; Shape memory alloy; Specific materials; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2008.09.012

Highly adherent tungsten-containing diamond-like carbon coating (W-DLC) was investigated. Two types of W-DLC coating are deposited onto a mirror-polished SMA substrate by PECVD and co-sputtering of the tungsten metal target. A DLC coating is also investigated for comparison. Uniaxial tensile tests are performed for these three types of coating and the peeled-off area is estimated visually. The best adherence was achieved with a WD40 film and the peeled-off area was estimated to be ~ 1% even after 10% tensile strain was applied to the coating. To evaluate the adhesive strength, scratching tests were carried out and, of the three, WD40 showed the highest adhesive strength. The higher adhesive strength of the DLC coating results from a reduction in internal stress and a lowering of coating hardness by the introduction of additional elements.