Environment-Friendly Functional Surface Treatment ENFUNSURF

Transcription

1 Environment-Friendly Functional Surface Treatment ENFUNSURF Helena Ronkainen VTT Technical Research Centre of Finland Impact Day

2 Environment-Friendly Functional Surface Treatment - ENFUNSURF Project Manager: Helena Ronkainen, VTT Technical Research Centre of Finland Period: Research partners: VTT Technical Research Centre of Finland: Helena Ronkainen, Kenneth Holmberg, Anssi Laukkanen, Simo Varjus, Tom Andersson International co-operation: Keio University: Prof. Tetsuya Suzuki Kanagawa Industrial Technology Center (KITC): Dr. Makoto Kano, Dr. Masao Kumagai, Takahiro Horiuchi, Kentaro,Yoshida Kanagawa Academy of Science and Technology: Dr. Hideyuki Kodama International extensions/links: Japan Science and Technology Agency (JST)

3 Environment-Friedly Functional Surface Treatment - ENFUNSURF Motivation: The DLC technology can provide excellent wear resistance and low friction properties both in dry and lubricated conditions. It is a promising coating for tribological applications to improve energy efficiency, but still more knowledge is required for the most demanding applications of the DLC coatings. Target: The objective of the project is to broaden the understanding of the diamond-like carbon (DLC) coatings by combining the knowledge and the research facilities in collaborating organizations and thus enhance the use of environmentally advantageous solutions based on DLC technology for industrial and consumer applications. Approach: Combining modeling and practical evaluation to deeper understanding of performance and influencing factors

4 Diamond-like carbon (DLC) coatings ta-c - tetrahedral amorphous carbon Deposited by filtered arc discharge Hardness: 66.8GPa ± 3.2GPa Modulus: 352.6GPa ± 14.6GPa ta-c a-c:h - amorphous hydrogenated carbon deposited by PACVD Hardness Modulus 25.4GPa ± 0.7GPa 212.4GPa ± 5.1GPa a-c:h 0.3 µm 0.6 µm ta-c x x 1.0 µm a-c:h x x x

5 Scratch test using FE: Application in fracture toughness & behavior evaluation Experimentally: loading history + failure characteristics (= crack field densities [accounting for different crack types]) Numerical model: produce a finite element model reproducing the loading history for extraction of field variables

6 3D FE modeling of coating-substrate systems 1st principal stress ta-c 0.3 m after 1.3 mm sliding Equivalent plastic strain

7 Effect of coating thickness on stresses 0.6 µm ta-c after 1.2 mm sliding Similar uniform stress through the coating, but higher thickness provides loadcarrying capacity (lower stress). Surface 0.3 µm below the surface Interface

8 Effect of coating thickness on the stress behaviour of ta-c and a-c:h coatings Characteristics of first principal stress field in ta-c and a-c:h coatings. s is the distance from plane of symmetry at the coating surface at the locale of maximum principal stress.

9 kgh3cs.dsf Crack generation and fracture performance of DLC coatings Scratch testing was used for studying the crack generation and fracture performance of the coating Determination of critical load values LC1 and LC2 Observation of crack generation. Scratch tests Macro-Scratch Diamond stylus Coating pulling Interface sliding Ploughing fracture friction plastic deformatio + + Stylus Diamond r = 200 µm Pre-load Loading rate Max. Load Sliding speed 2 N 50 N/min. 50 N 10 mm/min.

10 Critical load LC 1 [N] Critical Loads LC1 and LC2 for a-c:h and ta-c µm 0.6 µm LC1 ta-c > LC1 a-c:h 1 µm a-c:h ta-c a-c:h ta-c Sliding direction ta-c LC1 LC1 ta-c > LC1 a-c:h LC2 ta-c < LC2 a-c:h 30 a-c:h Critical load LC2 [N] µm 0.6 µm LC2 ta-c < LC2 a-c:h 1 µm ta-c ta-c a-c:h LC 0.3 µm < LC 0.6 µm > LC 1.0 µm a-c:h LC2

11 Pin-on-disc testing with increasing load Counter part: Al 2 O 3 ball, diameter 10 mm Load increased stepwise: 2 N -> 5 N -> 10 N -> 15 N -> 20 N Sliding distance: 200 m/load, 1000 m in total Sliding speed: 0.15 m/s

12 Wear surface analyses of DLC coatings

13 Friction performance of DLC coatings

14 Conclusions MAIN RESULTS: The ta-c coating experiences higher stress-state compared to a- C:H coating. ta-c is also more prone to coating thickness effects. Optimum film thickness found for the test geometry. For the a-c:h coating the mismatch between the coating and the substrate was smaller over the film thickness range studied leading to lower stresses. APPLICATIONS & IMPACT: Collaboration also covered information exchange and dissemination of project results and DLC technology in general Seminars in Finland and Japan Company visits in Finland and Japan