Michal Brazda

Scopus Publications

Stellite coating deposited by directed energy deposition
Jaroslav Vavřík, Taťána Hrbáčková, Pavel Salvetr, Michal Brázda
Metal 2020 29th International Conference on Metallurgy and Materials Conference Proceedings, 2020
This paper explores a protective stellite coating on 1.4922 martensitic steel. Stellite coatings are often used to improve the properties of the part's surface. The microstructure of the sample was analysed and its hardness measured. Protective coatings enhance mechanical and corrosion properties of the substrate, and thus extend the life of the respective part. They can be created by galvanizing, ion implantation, thermal spraying, or by more recent methods, such as laser cladding, DED (directed energy deposition) and others. DED is one of the metal deposition processes that fall in the AM category (additive manufacturing). It was used to deposit the protective coating in the present study. DED is an evolving technology which is suitable not only for prototype development, but also for promising applications involving surface treatment and repairs of functional parts. DED uses a laser beam as a thermal source to melt powder which is blown concentrically with the laser beam and the protective gas. The unique advantage of this method is a very good cohesion and bonding between the substrate and the deposited layer with a smaller HAZ (heat-affected zone). It produces comparatively few inhomogeneities and defects, which makes it a promising technique for protective layer applications. Stellite was chosen as a protective coating material because this group of alloys exhibits excellent properties such as high wear resistance, abrasion resistance, superior corrosion resistance and erosion resistance. These are relevant in many industrial sectors, such as power generation, aerospace and others. Stellite 21 was used in the present study.
Influence of laser power in direct laser deposition on the proportion of ferrite and austenite in duplex steel saf2507
Michal BRÁZDA, Pavel SALVETR, Jaromír DLOUHÝ, Jaroslav VAVŘÍK
Metal 2020 29th International Conference on Metallurgy and Materials Conference Proceedings, 2020
This work focuses on the effect of laser power on the proportion of austenite and ferrite in duplex steel SAF 2507. Duplex steels combine the advantages of ferritic and austenitic steels, preferably with an optimal proportion of austenite and ferrite. The effect of laser beam power in direct laser deposition on this proportion of microstructure constituents was studied. The proportion also has an impact on mechanical and corrosion properties, which are essential for this type of steel. Duplex steels are often used in corrosive environments and their mechanical properties and corrosion resistance depend on the proportion of austenite and ferrite. Direct laser deposition (DED) was used for making samples. DED operates on the principle of laser melting of a powder which is carried by the shielding gas into a nozzle. This technology can be used as an additive manufacturing process as well as for surface repairs and modification of components. The samples in this experimental study were printed using several different fixed outputs and the same intervals. One sample was printed using the machine's automatic mode. Microstructural analysis was performed using EBSD, EDS and light microscopy. The proportion of austenite and ferrite was measured by X-ray diffraction (XRD analysis). The differences in the proportion of ferrite and austenite were minimal, on the order of several percentage points.