Adhesive bonding and brazing of nanocrystalline diamond foil onto different substrate materials

• Published in: Applied surface science Vol. 282; pp. 335 - 341
• Main Authors: Lodes, Matthias A., Sailer, Stefan, Rosiwal, Stefan M., Singer, Robert F.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2013; Elsevier
• Subjects: Adhesion; Adhesive bonding; Adhesive strength; Adhesives; Aluminum; Brazing; Coating; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Diamonds; Exact sciences and technology; Foils; Hot filament chemical vapour deposition (HFCVD); Nanocrystalline diamond foil (NCDF); Physics; Scratch test; Steels; Strength; Hot filament chemical vapour deposition (HFCVD); Adhesives; Adhesion; Scratch test; Nanocrystalline diamond foil (NCDF); CVD; Diamonds; Nanocrystal; Film growth
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2013.05.129

•Successful joining of nanocrystalline diamond foil onto steel and aluminium.•Rockwell indentation gives good first evidence of the quality of adhesion.•Application of modified scratch test allows comparison of adhesion strength. Diamond coatings are used in heavily stressed industrial applications to reduce friction and wear. Hot-filament chemical vapour deposition (HFCVD) is the favourable coating method, as it allows a coating of large surface areas with high homogeneity. Due to the high temperatures occurring in this CVD-process, the selection of substrate materials is limited. With the desire to coat light materials, steels and polymers a new approach has been developed. First, by using temperature-stable templates in the HFCVD and stripping off the diamond layer afterwards, a flexible, up to 150μm thick and free standing nanocrystalline diamond foil (NCDF) can be produced. Afterwards, these NCDF can be applied on technical components through bonding and brazing, allowing any material as substrate. This two-step process offers the possibility to join a diamond layer on any desired surface. With a modified scratch test and Rockwell indentation testing the adhesion strength of NCDF on aluminium and steel is analysed. The results show that sufficient adhesion strength is reached both on steel and aluminium. The thermal stress in the substrates is very low and if failure occurs, cracks grow undercritically. Adhesion strength is even higher for the brazed samples, but here crack growth is critical, delaminating the diamond layer to some extent. In comparison to a sample directly coated with diamond, using a high-temperature CVD interlayer, the brazed as well as the adhesively bonded samples show very good performance, proving their competitiveness. A high support of the bonding layer could be identified as crucial, though in some cases a lower stiffness of the latter might be acceptable considering the possibility to completely avoid thermal stresses which occur during joining at higher temperatures.