Stability of DLC film on stainless steel investigated by tensile-test H. W. Choi1,2, K. -R. Lee, R. Wang3, K. H. Oh2 Future Technology Research Division, Korea Institute of Science and Technology Materials Science and Engineering, Seoul National University Department of Metals and Materials Engineering, University of British Columbia, Vancouver, Canada Introduction Biological application of DLC as a stent General Bio application of DLC Heart Valve DLC for Wear Resistance Courtesy of A-san hospital (’04.7.) ● Electrolytic-polishing ○ liquid : A2 ○ 15V, 19flow, 30Sec ● Processing parameters ○ Ar cleaning : 3mTorr, -600Vb, 15min-60min ○ Si buffer layer - 20m Torr, 60% MFC - -200Vb, 2min 30sec-15min ○ Annealing : at room-400°C ● DLC deposition ○ R.F-PACVD ○ C6H6, -400Vb, 10mTorr, 11min Purpose Experimental condition Estimated problem of DLC for bio application as a stent SUS 304 0.09-0.12mm Ar pre-cleaning (15-60min) Si buffer layer ( 2m30s – 15min) DLC ○ Biomaterial : Stainless steel ○ Disadvantage of metal substrate as a biomaterial - wear debris : cause foreign body reaction, tissue reaction - harmful ion ( Cr+, Ni+) can occurrence - metal corrosion can induce bone resorption SUS 304 Ar pre-cleaning Time & adhesion Experimental Results (a) 100μm (a) (b) (c) (d) (b) 20μm 20μm Ar -600Vb, 15min Ar -600Vb, 30min (c) 20μm (d) A direction of cracks followed the perpendicular against strain direction and spallation which seem to related to its slip band propagated with its shear stress Strain- Force curve of tensile test Ar -600Vb, 60min Bias voltage & adhesion Annealing & adhesion Si buffer thickness & adhesion Summary 20μm Stability of DLC films within 2% strain. However, Observed crack occurrence from 3.8% strain. A Relationship of adhesion depends on processing parameters. ◦ Improvement of adhesion with increasing Ar pre-cleaning time ◦ Enhancement of adhesion with increasing Bias voltage during Ar pre-cleaning. ◦ Increasing of adhesion with increasing Si buffer layer thickness ◦ Degradation of adhesion with increasing Bias voltage during Si buffer layer deposition ◦ Deterioration of adhesion with increasing Annealing temperature 20μm 20μm Ar -200Vb Ar -900Vb, No annealing Si -200Vb, 19nm 20μm Evolution of spallation ◦ Crack occurrence : Vertical of tensile direction ◦ Spallation evolution direction : shear stress direction 20μm 20μm Possibility of adhesion evaluation by tensile test. Ar -900Vb Ar -900Vb, 400°C annealing Si -200Vb, 84nm