Study On Friction And Wear Behavior Of Diamond-like Carbon Film In Water Environment

The development of new self-lubricating solid films to reduce the friction of mechanical components has great application significance due to the severe loss of material and energy caused by frictional wear,of which amorphous carbon-based films have been widely noted for their superior mechanical properties and tribological behavior.However,amorphous carbon-based films are now unable to meet the increasingly demanding working environment of mechanical components,and cannot give full play to the protection of mechanical components.In addition,although water has the advantages of being green,environmentally friendly,cheap,and readily available,there are also some bottlenecks in water-based lubrication technology,such as low viscosity,which may lead to insufficient lubrication during friction,and chemical reactions between water and metal components,leading to corrosion.Researchers have found that depositing thin films with elemental doping or structural design can result in films with superior tribological properties.Therefore,in this work,amorphous carbon-based films were deposited on the surface of 316L stainless steel using non-equilibrium magnetron sputtering equipment.In addition,B₄C has good tribological properties when water-lubricated.To enhance the water-lubricated effect of the amorphous carbon-based films,boron-doped amorphous carbon-based（DLC-B）films were obtained by modulating the current strength of the B₄C target when depositing the films.It is also found that H plays a great role in maintaining and achieving lubrication.Therefore,by modifying the DLC-B films with optimal tribological properties by regulating the gas flow rate（0,2,4,6,8,12 sccm）of the incoming isobutane,B and H co-doped DLC films were successfully prepared and the tribological behavior and synergistic lubrication mechanism of B and H co-doped amorphous carbon-based films in water-based lubrication were investigated,the main results of this study are as follows:（1）The DLC-B-0.5A films have excellent mechanical and frictional properties,and they achieve the best hardness,modulus of elasticity and the best bonding force.This is due to the high hardness and good wear resistance of B₄C ceramics,which improves the mechanical properties of amorphous carbon-based films by doping them with element B.The minimum stable coefficient of friction of the DLC-B film is approximately 0.06,and its excellent tribological behavior is attributed to the following:firstly,the doping of element B improves the structure,hardness and elastic modulus of the film;The second is the formation of a small amount of graphitized transfer film,silica gel,and boric acid on the worn surface of DLC-B film.（2）The DLC-B&H films exhibit the best hardness,elastic modulus and excellent bonding due to the appropriate amount of H doping which increases the content of sp³-CC bonds in the films and significantly improves the mechanical properties of the films.DLC-B&H/Si C friction substrate and DLC-B&H/Si₃N₄ friction substrate has excellent friction performance,mainly due to the presence of silicon oxide and boron oxide during the friction process in addition to a slight graphitic transformation at the friction interface,which further generates boric acid and silica with lubricating properties in the presence of water lubrication.According to the Gibbs free energy,Si C reacts with water to form silica gel,which has a lubricating effect and therefore achieves excellent frictional properties.（3）When the DLC-B&H thin films and Al₂O₃ balls rub against each other in an H₂O₂environment,although boric acid,a lubricating product,is generated,due to the high Hertz contact pressure,Al₂O₃ ball particles appear on the wear scar.As the friction process continues,abrasive wear occurs on the thin films,resulting in higher friction coefficients and wear rates for the thin films.