In-situ tensile testing of crystalline diamond coatings using Raman spectroscopy

In-situ SEM study of crack initiation, propagation and interfacial debonding of Ni-P coating during tensile tests: Heat treatment effect

“…It brings out tunnel cracks emanating from the top surface of the coating toward the inner wall and stopping at the substrate. Thus, it is very interesting to observe a strong adhesion of the coating to the substrate, which can be deduced from the high brittleness and the less strength of the coating [20,32,41]. These cracks are very opened and present flat faces due to Mode I crack opening.…”

“…As discussed in the introduction, the mechanism of crack formation in the coating can be related to the fact that the shear stress present at the interface between the metallic substrate is transferred to the coating during tensile loading. This shear stress reaches its maximum and rises the stress level in the coating to the fracture stress and causes cracks in the coating [19,20].…”

“…The evaluation of this adhesion was essential to characterize the strength of composite. Several methods were used to quantify the adhesion between the coating and the substrate [9][10][11][12][13][14][15][16][17][18][19][20], including three [9] or four bend tests [10,11], tape and pull-out tests, indentation [12,[13][14][15][16] and scratch techniques [9]. Nevertheless, the accuracy of these methods is compromised by the presence of a third body.…”

“…Chen [17] and others revealed that four sequentially morphologies of the crack were observed on the surface of coating: multiplication, stabilization, cross-linking and spallation [26,21]. On the contrary, others have reported that the debonding of coating would occur following the saturation of parallel cracks [19,20,22,[28][29][30]. This dissimilarity could be attributed to the adherence between two the materials.…”

“…However, the roughness of the substrate under a tensile test has not taken into consideration to study the failure strain of coating. This remark is intriguing since numerous studies have interpreted that the spallation occurs when the surface of substrate is more rugged and developed than the coating [17,20]. Hamad et al [32] revealed that the stress transferred from the substrate to the coating segments was dependent on the elastic and elastic/plastic properties of the coating and the substrate.…”