Improved surface properties of β-SiAlON by diamond-like carbon coatings

β-SiAlON ceramics have potential for biomedical implants but they suffer due to moderate hardness and high surface roughness. Attempts have been made to improve the hardness and surface properties by coating diamond-like carbon (DLC) on β-SiAlON ceramics using radio frequency-plasma-enhanced chemical vapor deposition. By optimizing the self-bias and bonding environment, we report the deposition of very hard (43.4GPa) and ultra smooth (surface roughness 0.47nm) DLC coating on β-SiAlON at a self-bias of −140V. Compared with uncoated β-SiAlON, DLC coated β-SiAlON show three times increment in hardness and ten times reduction in surface roughness. When the self-bias is changed, nano-mechanical properties of such DLC coated β-SiAlON ceramics, however, got modified, which correlated with the bias induced structural changes. When the indentation load is increased from 3 to 10mN, hardness decreased significantly due to increase in substrate (or ceramic) effect. Owing to high hardness, high wear resistance and low surface roughness, DLC coated SiAlON structure can find wide biomedical applications such as prosthetic hip joint replacement.