Harsh Sliding Wear of a Zirconia Ball against a-C:H Coated CoCrMo Disc in Hyaluronic Gel

Harsh Sliding Wear of a Zirconia Ball against a-C:H Coated CoCrMo Disc in Hyaluronic Gel

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The a-C:H (amorphous carbon-hydrogen) films belong to the family of DLC (diamond-like carbon) coatings.The a-C:H coating was deposited on medical grade CoCrMo substrates by plasma-assisted chemical vapor deposition (PA-CVD) using benzene as gaseous precursor.Benzene offers an aromatic read more structure, which affects the a-C:H properties after plasma decomposition.A zirconia ball was sliding at two different frequencies, 50 Hz or 1Hz, against the uncoated and a-C:H coated CoCrMo.The frequency of 1 Hz is typical for human movement during fast walking.

The harsh sliding conditions with a normal load of 100 N and 50 Hz frequency simulate extreme overloading of the biomedical sliding partners.It gives insight into the failure mechanisms.The wear tests were carried out in laboratory air (dry, RH: 15.6%) or using hyaluronic gel as lubricant.The hyaluronic gel acts as an effective intermediate medium.

It adheres very well to both, a-C:H coating and zirconia.No wear was evident on the ZrO2 ball at 1 Hz and 100 N.Minor wear traces were observed on the a-C:H coating only.A wear coefficient of 0.16 × 10−6 mm3/N·m were calculated for a-C:H coated CoCrMo after ZrO2 ball sliding with 1 Hz and 100 N in hyaluronic gel.

This is two orders of magnitude lower aluminum lotion in comparison to dry sliding of ZrO2 ball against DLC coated CoCrMo with 1 Hz.The coefficient of friction (COF) remained below 0.09 until the hyaluronic gel starts to lose viscosity.This finding pronounces the importance of a proper homogeneous lubrication during operation of the biomedical joints.For extreme harsh tribological loading like sudden jumps of a patient with artificial joints, the application of an intermediate layer before a-C:H coating needs further evaluation.