나노결정질 다이아몬드가 코팅된 SiC 마모시험기 볼

Abstract

Nanocrystalline diamond(NCD) coated SiC balls were applied in a ball-on-disk tribometer. After seeding in an ultrasonic bath containing nanometer diamond powders, 2.2 μm thick NCD films were deposited on sintered 3 mm diameter SiC balls at 600oC in a 2.45 GHz microwave plasma CVD system. Bare ZrO2 and SiC balls were prepared for comparison as test balls. Tribology tests were performed in air with pairs of three different balls and mirror polished steel(SKH51) disk. The wear tracks on balls and disks were examinedby optical microscope and alpha step profiler. Under the load of 3 N, the friction coefficients of steel againstZrO2, SiC and NCD-coated balls were between 0.4 and 0.8. After a few thousands sliding laps, the frictioncoefficient of NCD-coated balls dropped from 0.45 to below 0.1 and maintained thereafter. Under a higherload of 10 N or 20 N with a long sliding distance of 2 km, ZrO2 and SiC balls exhibited the similar frictioncoefficients as above. The friction coefficient of NCD-coated balls was less than 0.1 from the beginningand increased to above 0.1 steadily or with some fluctuations as sliding distance increased. NCD coatinglayers were found worn out after long duration and/or high load sliding test, which resulted in the frictioncoefficient higher than 0.1.