TITANIUM NITRIDE AND DIAMOND LIKE CARBON COATINGS FOR CARDIOVASCULAR APPLICATIONS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 679

TABLE 21.4. Surface Roughness Profi les of Coated and Uncoated Samples

Ra ( μ m)

Material surface Mean SD

UHMWPE 0.13 0.04

DLC coated UHMWPE 0.25 0.05

Ti6Al4V 0.07 0.01

TiN coated Ti6Al4V 0.08 0.02

Cp Titanium 0.06 0.02

DLC coated Cp Titanium 0.06 0.01

TABLE 21.5. Pin - on - Wheel Test Conditions

Parameter Unit Value

Relative motion — Circular sliding

Sliding speed mm/sec 55 ± 2.5

Duration of test hours 6

Contact stress Kg/cm 2 14 ± 1

Lubricant — None

Temperature ° C 30 ± 3

Initial surface roughness μ m Ra < 0.2

Figure 21.3. Pin-on-Wheel adhesive wear test results: weight loss from UHMWPE wheel when
traversed against (a) Titanium (b) DLC-coated titanium and (c) TiN-coated titanium pins. The
wear from the UHMWPE is reduced by the introduction of the coating on the counter face.

between the coating and the substrate. The inter-molecular adhesion between the
coating material and the substrate will always be lesser than the attractive forces
between the substrate molecules. This lower coating adhesion when challenged
by an abrasive material tends to give way and causes erosion or peeling of the
coating. The adhesion studies were carried out on the coated surfaces to estimate
the typical force range in which the coating integrity is maintained.