Failure mechanism and protective role of ultrathin ta-C films on Si (100) during cyclic nano-impact

Dynamic fracture of CrN coating by highly-resolved nano-impact

“…All of the data except vin for CrN coating exhibit larger error bars than the substrate, which may be caused by the formation of some micro-cracks in the coating during the impact process. It has been shown recently [35] that the onset of variability in repetitive impact tests can provide a useful additional metric for the onset of cracking. At 10 mN there is very good consistency in hm on CrN/HSS but at 30 mN there is greater test-to-test variability, suggetive of cracking in at least some of the tests at this load.…”

Dynamic Impact Resistance and Scratch Adhesion of AlCrN Coatings Sputtered Using Cathodic Arc Glow Discharge

“…Zone I: With the first impacts, the V C increases mainly due to the substrate plastic deformation [38], whereas the coating is elastically stressed [13]. As the extent of plastic deformation increases after every successive impact, the contact pressure rapidly decreases because of the increasing contact area between the impact ball and sample.…”

“…Zone II: When the contact pressure decreases to the substrate yield point, the plastic deformation of the substrate is suppressed and the system transits into zone II, the "zero impact wear" stage [11]. The V C remains almost constant with increasing impact cycles [11,38]. In this zone, the contact pressure is almost stable, and the cyclic impact loads provide the stress necessary for crack nucleation, propagation, and coalescence [40].…”

“…In this zone, the contact pressure is almost stable, and the cyclic impact loads provide the stress necessary for crack nucleation, propagation, and coalescence [40]. Accordingly, the edge cracks initiate from the coating surface and propagate downwards towards the interface, while the lateral cracks initiate at the substrate/coating interface and propagate upward into the coating [38,40].…”

“…Zone III: After the zero-impact wear stage, the coating/substrate system cannot accumulate more energy received from an impact indenter; hence the system transits into zone III. In this stage, the cohesive failure of the film and/or adhesive failure at the interface occurs, and the V C increases rapidly with increasing impact cycles [38].…”