Surface modification of Co-Cr-Mo alloy by plasma assisted CVD

Abstract

Co-Cr-Mo alloy is a key material of total joint replacements. Ions releases (corrosion) in addition to Wear are a common failure mechanism in metal-on-metal (MOM). One of many new methods to coating DLCs is Plasma assisted chemical vapor deposition (PACVD) technique. Using PACVD to coat Co-Cr-Mo alloy is a new technique needs many research to allow for using in biomedical applications. DLCs provides smooth morphology surface. That morphology is reducing of surface roughness improvement tribological behavior. Using a best condition of coating parameters are Acetylene gas flow rate 40 sccm and voltage is 1600 v with Voltage between electrodes is 250 v for (PACVD) results coating film with 83% diamond like carbon (sp3) with thickness is 100 μm. Observations of surface indicate by suing both SEM and AFM indicate no crack and smooth surface with surface roughness is 0.679 µm in DLCs. Raman tested to determine the amount diamond like carbon (sp3) is 83%.that meaning the minimum of hydrogen content. Hardness tested to indicate increasing up to three times. The hardness of coating samples is 11.77 Hv, while in substate was about 3.923 Hv. Corrosion test by using simulated body fluid solution. DLCs improved the corrosion resistance of Co-Cr-Mo alloy with semi-body fluid solution. The samples have spontaneously passive in semi-body fluid solution at current density is 32.6 × 10−6 A/cm2 at potential is −416.5 mV for uncoated sample. While for DLCs current density is 3.92 × 10−6 A/cm2 with the potential of −35.5 mV. From comparing the maximum current for both samples shows the density for uncoated more than the DLCs, it is 207 and 11.1 mA/cm2 respectively. This reduction of the current densities explains improvement of corrosion resistance due to the surface modification by DLCs. Also, the reduced of electron conductivity of DLCs in comparison to uncoated sample indicate low electrical conductivity of the DLCs. That reduces the electron transport and the exchange of electrical charges at the samples surface, which is necessary for the electrochemical corrosion. In addition, reduces the Ni ion release of alloy.