In this study, the stress state of metal coating on a steel substrate under tensile straining was investigated by with finite element modelling with the aim of better understanding the mechanism of delamination for the coating. The investigations showed cracking and delamination of the coating by the application of uniaxial tensile strain to the substrate. Due to interfacial stress crack appeared in the coating-substrate interface. The stress measurements in coated substrate, using FEA, indicated interfacial shear and peeling stresses at the interface near the edges of the coating under tensile load. When tensile stress is applied externally on the coated substrate, the coating exhibits multiple cracking perpendiculars to the tensile direction, and then interfacial debonding occurs. A good agreement is found between the modelling approach and the corresponding experimental tensile tests of the coated specimens. The effect of coating thickness on the evolution of the stress distribution was also studied. The cracking and delamination of the coatings with a thickness ranging from 90 to 160 m was studied by tensile test experiments. The estimation of the stress distribution and concentration at the interface during these experiments allows the failure stress of the coating in the interface coating–substrate to be evaluated.
Author: N. Tonchev
The paper contains results for wear in conditions of impact between a standard welded and tested specimen realized in the presence of a layer of abrasive particles trailing in the contact zone. It gives an idea about the specifics of this type of wear depending on the impact force and the particle size of the abrasive at various hardness achieved by hard-facing with alloys with different carbon equivalent and a degree of hardening of the layer after the test. Based on an experimental research it was proved that the impact-abrasive wear has its specific features expressed via respective graphical relations. The research was funded by Fund “Scientific Research” at the Ministry of Education and Science of the Republic of Bulgaria.