Doping Non-carbide Formed Metals For Improving Toughness Of Diamond-like Carbon Films

With the purpose of improving the toughness of diamond-like carbon (DLC) film,on the basis of the coating concept of Metal containing DLC (Me-DLC) film,silver-containing diamond-like carbon films (Ag-DLC) and copper containingdiamond-like carbon films (Cu-DLC) with different metal contents were depositedusing ion beam assisted deposition (IBAD) and mid-frequency dual-magnetronsystem. The film toughness was revealed by systematic investigation of the influenceof the incorporation of non-carbide formed metals on the microstructure, mechanicalproperties and combined tribological performances. A methodology employed tomeasure toughness for thin films was also discussed. The results were shown asfollowed:(1) Ag-DLC films of six Ag contents on M2high speed steel substrate weredeposited with in an IBAD system. The toughness of the deposited films was revealedby systematic investigation of the influence of Ag content on the adhesion andimpact-resistant properties. Results verified that the doping of silver distinctlyinfluenced the toughness of Ag-DLC films. Typically:(i) the variation of Ag contentsand nanocrystallites dispersed in the DLC matrix tended to induce change of filmtoughness as a result of changing the film adhesion and impact-resistance behaviors;(ii) the evidence of improvement in the toughness of the film (especially for the filmcontaining15.2at%silver) could be clearly seen by the larger critical adhesion forces,and the better adhesion performance and impact resistant properties. The failuremechanisms of both scratch and impact tests served to reveal how the toughness of the Ag-DLC films was affected by Ag content.(2) Cu-DLC films of five Cu contents on Si (100) substrate were deposited with inan IBAD system. Variation of Cu content and nanocrystallites dispersing in DLCmatrix induces corresponding modification in film toughness as well as hardness,intrinsic stress and sliding frictional behavior, resulting in improvement of filmtoughness for the combined tribological performances. The film toughness wasinvestigated by scratch crack propagation resistance from the critical load dataobtained from scratch test. Results revealed that doping Cu with nanograin sizes,especially at a suitable content of10.5at%will significantly improve the crackinitiation resistance and propagation resistance of crack during scratch test,demonstrating the improved toughness.(3) Cu-DLC films were coated on Mg alloys in a mid frequency dual-magnetronsystem. Variation of Cu content and nanocrystallites induces corresponding changesin film mechanical properties and biomedical properties:(i) a:C–Cu11.4%film showshighest hardness, low internal stress and best adhesion properties; a:C–Cu8.7%filmexhibits the best hemocompatibility property, the protective ability of the film for Mgalloys were revealed by a rather low coefficient of friction and wear rate in simulatedbody fluid conditions as well as good corrosion-resistant in NaCl solution.