Resumen de Effect of the temperature on the microstructure and the mechanical properties of laser cladded Ni-based metal matrix composite coatings
Ni-base superalloys are usually adopted in applications where the corrosion and the oxidation resistance is critical for the correct service of a mechanical part, i.e., in drilling and oil extraction, mining, thermoelectric plants, steam turbine, aircraft engines, etc. However, these alloys have a low resistance to wear and, in all the previously listed applications, static and dynamic parts are subjected to erosive processes, for example due to hard particles, like oxides, coming from the outside or directly generated in the system, that could hit and scratch the different parts promoting undesirable failures.
Cermets and Metal Matrix Composites (MMC) are innovative solutions that combine the best properties of metals and ceramics to improve the characteristics and the service life of engineering components, i.e., toward higher working temperature or higher wear load. In these materials, the metal works as a bonding for the ceramic parts and reduce in this way the brittle behaviour of the final component.
While thermal spray techniques, in particular High-Velocity Oxy-Fuel Spraying (HVOF) and Plasma Spray (PS), are the most common methods to process composite coatings, with the appearance of high-power lasers, the Laser Cladding (LC) technique is a very efficient alternative in technical and also economical terms.
The research work performed and described in this thesis evaluates the effects to introduce Cr3C2 chromium carbide ceramic particles in a Ni-base superalloy matrix, analysing the variation of the microstructure, mechanical properties and local wear behaviour. Two different systems were studied: an Inconel 625 (IN625) alloy coating, and the matrix of a MMC coating constituted by Inconel 625 and Cr3C2 (IN625-Cr3C2). Both superficial layers were applied onto a steel substrate by LC using a High-Power Diode Laser (HPDL). In addition, the effects of the exposition at high temperature were studied to find a relationship between the evolution of their microstructure, mechanical properties and local wear behaviour. The mechanical properties were studied by Depth Sensing Indentation (DSI) tests and the wear behaviour by local scratch tests.
