Improved adhesion of a-C and a-C:H films with a CrC interlayer on 16MnCr5 by HiPIMS-pretreatment

• Published in: Surface & coatings technology Vol. 375; pp. 877 - 887
• Main Authors: Tillmann, Wolfgang, Lopes Dias, Nelson Filipe, Stangier, Dominic, Maus-Friedrichs, Wolfgang, Gustus, René, Thomann, Carl Arne, Moldenhauer, Henning, Debus, Jörg
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.10.2019; Elsevier BV
• Subjects: Adhesion; Adhesive strength; Amorphous carbon; Carbon; Chromium carbide; Chromium manganese steels; Hardness tests; HiPIMS; Indentation; Interlayers; Ion etching; Magnetron sputtering; Plasma; Pretreatment; Scratch tests; Sputtering; Substrate/film interface; Substrates; Surface pretreatments; HiPIMS; Chromium carbide; Amorphous carbon; Substrate/film interface; Adhesion; Sputtering
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2019.07.076

Ensuring a high adhesion of amorphous carbon films to steel substrates remains a challenging task, sustaining continuous research efforts to improve the adhesion strength. Besides the interlayer system and the substrate material, surface pretreatments have a significant impact on the adhesion behavior. Within this context, the influence of the High Power Impulse Magnetron Sputtering (HiPIMS) pretreatment on the adhesion of magnetron sputtered hydrogenfree (a-C) and hydrogenated (a-C:H) amorphous carbon films with a chromium carbide (CrC) interlayer on 16MnCr5 steel is investigated. The plasma treatment consisted of 30 min Ar ion etching as well as a sequential 5 min of HiPIMS-pretreatment with a Cr cathode. Subsequently this pretreatment was compared to a procedure without utilizing the HiPIMS technique. The impact of the HiPIMS-pretreatment on the structure of the film was systematically analyzed by taking the CrC interlayer as well as the entire film structure into consideration. The adhesion strength of the a-C and a-C:H films is significantly improved by the formation of a Cr HiPIMS-nanolayer in the substrate/film interface. In scratch tests, the critical load Lc3 for a total film delamination increases from 43 ± 4 to 59 ± 3 N and from 48 ± 2 to 64 ± 3 N for the a-C and a-C:H film. The improved adhesion behavior of the carbon films is ascribed to the increased adhesion of the CrC interlayer, which did not delaminate when scratched with a load up to 159 ± 18 N. Complementary Rockwell indentation tests reveal that the HiPIMS-pretreatment improves the adhesion class from HF6 to HF4 and from HF5 to HF3 for a-C and a-C:H. The enhanced adhesion is essential to exploit the properties of a-C and a-C:H films in applications with high loads. In conclusion, the HiPIMS-pretreatment has proven to be a promising technique to increase the adhesion strength of carbon films. [Display omitted] •Sputtered film structures consisting of CrC interlayer and a-C or a-C:H•HiPIMS-pretreatment using a discharge on the Cr target•Formation of a Cr HiPIMS-nanolayer in the substrate/film interface affects adhesion•Adhesion strength of CrC on HiPIMS-pretreated 16MnCr5 is significantly increased•Improved adhesion of CrC interlayer results in increased adhesion of carbon films