PhD ceremony Mr. I. Hemmati: Laser-deposited metallic coatings. Processing, characterization, alloy development

PhD ceremony: Mr. I. Hemmati, 14.30 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Laser-deposited metallic coatings. Processing, characterization, alloy development

Promotor(s): prof. J.T.M. de Hosson

Faculty: Mathematics and Natural Sciences

Laser cladding (also called laser deposition) and its related technologies are used to deposit protective coatings, repair damaged components and manufacture 3-dimensional objects. In this technique, the energy from a high-power laser beam is used to melt and deposit the coating material on a substrate. In this way, dense coatings with strong connection to their substrate are produced. Various types of coating materials including steels, nickel and cobalt alloys and metal-ceramic composites are used in laser cladding. In this thesis, the effects of processing conditions and alloy chemistry on microstructure and properties of laser-deposited coatings were studied. A range of microscopy techniques (including electron and optical microscopy) were employed to characterize the microstructure, cracking mechanism and phase constitution of the coatings. The cracking problem in laser-clad coatings was investigated in detail and some solutions were provided for it. In addition, functional properties of the coatings such as hardness, wear and corrosion resistance were evaluated. These findings were correlated to establish the processing-microstructure-properties relationships which helped to develop new nickel-base alloys. These new alloys could produce coatings with better performance in comparison to that of the commercial counterparts. The final goal of this work was to create the technical know-how of laser cladding to produce coatings for marine applications such as dredging industry. Laser cladding technology proved to be a suitable method to replace the currently used coatings in marine applications and in similar industries.