We are pleased to announce that the Scientific Council of the IPPT PAN has awarded Piotr Jenczyk the degree of Doctor in Engineering and Technical Sciences, in the discipline of Mechanical Engineering. The title of his dissertation is: “Modification of the Matrix–Reinforcement Interface in Ni–SiC Composites to Improve Their Tribo-Mechanical Properties”.
The dissertation was supervised by Assoc. Prof. Dariusz Jarząbek, with Szymon Nosewicz, PhD serving as assistant supervisor.
Modification of the Matrix–Reinforcement Interface in Ni–SiC Composites to Improve Their Tribo-Mechanical Properties
Metal–ceramic composites combine the hardness and wear resistance of the ceramic phase with the ductility of the metallic matrix, making them useful in many modern technologies. In particular, such composites in the form of coatings are used to improve the wear resistance of components such as pistons or turbines.
The aim of the research presented in the dissertation was to increase the wear resistance of nickel–silicon carbide coatings by improving the bonding strength between the matrix and the reinforcement. This was intended to be achieved by applying a thin protective layer to the ceramic particles reinforcing the metallic composite. The coating modifies the way the metallic matrix bonds with the reinforcement particles, thus affecting the tribological properties of the entire composite. The matrix–reinforcement interface was examined using a novel method developed as part of this dissertation. This method combines advanced experimental techniques with numerical modeling to determine the mechanical strength of the matrix–reinforcement bond. Techniques employed include focused ion beam milling, micro-beam bending, and atomic force microscopy for fracture surface characterization. The experimental data were then used to construct a finite element model incorporating cohesive elements. Additional methods used in this work include nanoindentation, energy-dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). Wear resistance was also tested using a ball-on-flat reciprocating motion setup.
The main outcome of this dissertation is the demonstrated increase in the wear resistance of Ni–SiC composite coatings due to the application of a protective layer. At the same time, the protective coating did not enhance the bonding strength between the matrix and the reinforcement. Furthermore, a decrease in nickel grain size with increasing reinforcement content was observed, as well as local grain coarsening of nickel in the vicinity of reinforcement particles, influenced by the protective layer.
The conducted research led to the conclusion that the protective layer ensures a more uniform distribution of reinforcement particles within the composite, thereby increasing wear resistance even though the interfacial bonding strength between the matrix and reinforcement decreases.
