The effect of substrate surface roughness on the wear behaviour of diamond-like carbon (DLC) coatings deposited on M42 tool steel substrate with composite interlayers has been investigated on a ball-on-disk wear rig in dry air. After deposition, the surface roughness of the coating was approximately half of the original substrate surface roughness. While the frictional behaviour was not apparently affected, the wear rate of the coatings increased significantly with increase in the substrate surface roughness. Wear rate increased rapidly when the substrate surface roughness exceeded Ra 0.93 μm. Above this substrate roughness, the dominant wear mechanism also changed from adhesion to chip/flake formation and fragmentation of the coatings. Chipping/flaking of the coatings initially occurred mainly at the tops of asperities of the surface texture. The Archard specific wear rate increased with increase in total load for coatings on the rough substrate surfaces; however, this was almost invariant with increase in load for coatings on the smoother substrate surfaces, nominally following the Archard’s wear law. Contact pressure distributions over the real area of contact between the ball and the rough coating surfaces have been analysed by applying the elastic foundation model of contact mechanics. It has been shown that the contact pressures increase significantly with increase in surface roughness of the coatings. The observed apparent effect of surface roughness on wear and wear mechanism transitions of the DLC coatings can be explained according to the contact mechanics analysis results.
DLC has proved to have excellent bio-compatibility as well. This has enabled many medical procedures, such as Percutaneous coronary intervention employing brachytherapy to benefit from the unique electrical properties of DLC. At low voltages and low temperatures electrodes coated with DLC can emit enough electrons to be arranged into disposable, micro-X-ray tubes as The effect of substrate surface roughness on the wear behaviour of diamond-like carbon (DLC) coatings deposited on M42 tool steel substrate with composite interlayers has been investigated on a ball-on-disk wear rig in dry air. After deposition, the surface roughness of the coating was approximately half of the original substrate surface roughness. While the frictional behaviour was not apparently affected, the wear rate of the coatings increased significantly with increase in the substrate surface roughness. Wear rate increased rapidly when the substrate surface roughness exceeded Ra 0.93 μm. Above this substrate roughness, the dominant wear mechanism also changed from adhesion to chip/flake formation and fragmentation of the coatings. Chipping/flaking of the coatings initially occurred mainly at the tops of asperities of the surface texture. The Archard specific wear rate increased with increase in total load for coatings on the rough substrate surfaces; however, this was almost invariant with increase in load for coatings on the smoother substrate surfaces, nominally following the Archard’s wear law. Contact pressure distributions over the real area of contact between the ball and the rough coating surfaces have been analysed by applying the elastic foundation model of contact mechanics. It has been shown that the contact pressures increase significantly with increase in surface roughness of the coatings. The observed apparent effect of surface roughness on wear and wear mechanism transitions of the DLC coatings can be explained according to the contact mechanics analysis results.
DLC has proved to have excellent bio-compatibility as well. This has enabled many medical procedures, such as Percutaneous coronary intervention employing brachytherapy to benefit from the unique electrical properties of DLC. At low voltages and low temperatures electrodes coated with DLC can emit enough electrons to be arranged into disposable, micro-X-ray tubes as small as the radioactive seeds that are introduced into arteries or tumors in conventional brachytherapy. The same dose of prescribed radiation can be applied from the inside, out with the additional possibility to switch on and off the radiation in the prescribed pattern for the X-rays being used. DLC has proved to be an excellent coating to prolong the life of and reduce complications with replacement hip joints and artificial knees. It also has been successfully applied to coronary artery stents, reducing the incidence of thrombosis. The implantable human heart pump can be considered the ultimate biomedical application where DLC coating is used on blood contacting surfaces of the key components of the device.
small as the radioactive seeds that are introduced into arteries or tumors in conventional brachytherapy. The same dose of prescribed radiation can be applied from the inside, out with the additional possibility to switch on and off the radiation in the prescribed pattern for the X-rays being used. DLC has proved to be an excellent coating to prolong the life of and reduce complications with replacement hip joints and artificial knees. It also has been successfully applied to coronary artery stents, reducing the incidence of thrombosis. The implantable human heart pump can be considered the ultimate biomedical application where DLC coating is used on blood contacting surfaces of the key components of the device.
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