1. 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 mm
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