Paulína Zacková, Lucia Števlíková, Ľubomír Čaplovič, Martin Sahul and Vitali Podgurski
The contribution deals with analysis of the influence of the substrate surface laser ablation before deposition process to improve the adhesion of coating-substrate system. The coatings were applied to the high-speed steel 6-5-2-5 (STN 19 852) and WC-Co cemented carbide with cobalt content of 10 wt%. LAteral Rotating Cathodes (LARC®) process was chosen for evaporation of individual CrN layers. Influence of laser ablation on the substrate morphology, structure, roughness, presence of residual stresses inside the substrates and layers and their adhesion behavior between the layers and the base material was studied. Scanning electron microscopy fitted with energy dispersive spectroscopy was utilized to investigate morphology and fracture areas of substrates with CrN layers. X-ray diffraction analysis was employed to detect the residual stresses measurements. Adhesion between the coatings and substrate was analyzed using “Mercedes” testing.
Edina Kocsisová, Mária Dománková, Ivan Slatkovský and Martin Sahul
Intergranular corrosion (IGC) is one of the major problems in austenitic stainless steels. This type of corrosion is caused by precipitation of secondary phases on grain boundaries (GB). Precipitation of the secondary phases can lead to formation of chromium depleted zones in the vicinity of grain boundaries. Mount of the sensitization of material is characterized by the degree of sensitization (DOS). Austenitic stainless steel AISI 316 as experimental material had been chosen. The samples for the study of sensitization were solution annealed on 1100 °C for 60 min followed by water quenching and then sensitization by isothermal annealing on 700 °C and 650 °C with holding time from 15 to 600 min. Transmission electron microscopy (TEM) was used for identification of secondary phases. Electron backscattered diffraction (EBSD) was applied for characterization of grain boundary structure as one of the factors which influences on DOS.
Marcel Kuruc, Martin Sahúl, Marek Zvončan, Jozef Peterka and Ľubomír Čaplovič
Titanium alloys are utilized especially in applications that require a good combination of high strength, low mass and good corrosion resistance in aggressive environments. However, mechanical properties prejudge titanium alloys to hard machinability. Machining of titanium alloys is usually accompanied by cooling with liquids or gasses. One of the most effective cooling approaches is cooling by liquid nitrogen. Liquid nitrogen decreases temperature of tool, but also increases strength, hardness and brittleness of workpiece. One of the most suitable machining methods to machine hard and brittle materials is ultrasonic machining. In this article, rotary ultrasonic machining of titanium alloys under cryogenic conditions is analyzed.
Martin Sahul, Paulína Zacková, Ľubomír Čaplovič, Kristián Šalgó, Jana Bohovičová and Jozef Sondor
The contribution deals with comparison of oxidation resistance of classical TiAlN monolayer coating and its advanced high hard nanostructured and multilayered nACo3 version at elevated temperatures. Both coatings were deposited onto AISI M36 high speed steel using unique LAteral Rotating Cathodes process (LARC®). “In - situ” X-Ray diffraction analysis was employed for determination of the beginning of oxides creation and phase detection at different heating temperatures. Scanning electron microscopy fitted with EDX analysis was used for observation of fracture areas and measurements of coatings and oxide layers thicknesses as well. Determination of chemical composition of coatings surfaces and elemental linescans through the coatings and oxide layers were performed using EDX analysis. All measurements of these coatings were carried out not only before but also after the thermal annealing.