Andrej Czán, Igor Daniš, Jozef Holubják, Lucia Zaušková, Tatiana Czánová, Matej Mikloš and Pavol Martikáň
Quality of machined surface is affected by quality of cutting process. There are many parameters, which influence on the quality of the cutting process. The cutting temperature is one of most important parameters that influence the tool life and the quality of machined surfaces. Its identification and determination is key objective in specialized machining processes such as dry machining of hard-to-machine materials. It is well known that maximum temperature is obtained in the tool rake face at the vicinity of the cutting edge. A moderate level of cutting edge temperature and a low thermal shock reduce the tool wear phenomena, and a low temperature gradient in the machined sublayer reduces the risk of high tensile residual stresses. The thermocouple method was used to measure the temperature directly in the cutting zone. An original thermocouple was specially developed for measuring of temperature in the cutting zone, surface and subsurface layers of machined surface. This paper deals with identification of temperature and temperature gradient during dry peripheral milling of Inconel 718. The measurements were used to identification the temperature gradients and to reconstruct the thermal distribution in cutting zone with various cutting conditions.
Piotr Kieruj, Damian Przestacki and Tadeusz Chwalczuk
This paper presents the analysis of emissivity engineering materials according to temperature. Experiment is concerned on difficult to machine materials, which may be turned with laser assisting. Cylindrical samples made of nickel-based alloys Inconel 625, Inconel 718, Waspaloy and tungsten-carbides based on cobalt matrix were analyzed. The samples’ temperature in contact method was compared to the temperature measured by non-contact pyrometers. Based on this relative, the value of the emissivity coefficient was adjusted to the right indication of pyrometers.
The purpose of this study was to assess the effect on selected mechanical properties, of adding recast materials to the NiCrMo alloy of newly produced castings.
Three groups of dental alloy NiCrMo (trade named Remanium CS+) were prepared by mixing 50% new alloy to alloy remnants from previous castings. The specimens in the first casting group used 100% new alloy and served as control (C1). The second group consisted of equal amounts of new alloy and alloy remnants cast only once (C2). The third group contained 50% of new alloy and alloy cast twice (C3). Microstructural analysis was performed and the chemical composition, hardness and the metal-ceramic bond strength were assessed. In addition, EDS analysis (mapping) was undertaken. Hardness and bond strength results were also statistically analysed.
In spite of the fact that recasting brought about small changes in hardness and chemical composition (C, Cr and Mo), these effects were found to not affect their functional properties in the oral cavity. Still, significant differences between new alloy and the recasted groups (p < 0.05) were demonstrated in the course of statistical analysis of Vickers hardness test (for α = 0.05). All analysed research groups have a similar average adhesion at 48.51÷49.24 MPa (p > 0.05).
The recasting procedure described in the paper can be done safely in dentistry. If previously casted material is used, it should be mixed with new material. The use of the material prepared in this way can lower the costs of NiCrMo castings.
Andrej Czán, Michal Šajgalík, Anton Martikáň and Jozef Mrázik
To generally improve effectivity of parts production and metal cutting process, there are used process models of super alloys together with finite element modeling simulations. Advanced measurement methods of the process could improve and verify the accuracy of these models. These methods cause many error sources when using empiric or exact methods such as infrared radiation thermography to measure the temperature distribution of the tool, workpiece, and chip during metal cutting. Measuring of metal machining is challenging due to factors such as the high magnification required, high surface speeds and deformations, micro-blackbody effects, changing emissivity and deformations present at metal cutting. As part of an ongoing effort to improve our understanding of uncertainties associated with these measurement methods, multimeasurement sets of experiments were performed. First set of measurements observed connection between surface temperature and the internal temperature of the cutting tool. This was accomplished by measuring the temperature using a thermal camera in cutting zone. Second set performed high-speed scan of dynamic processes such as formation of elastic and plastic deformation. During this operation was applied high-speed scannning system using macro conversion lens for monitoring of micro-structural changes in deformation areas. Next necessary applied set is recording of dynamic processes by implementation of piezoelectric measurement device for monitoring of cutting forces. The outputs from multimeasuring system are the basis for verification of theoretical knowledge from this field and elimination of uncertainties, which arise by using computer simulation systems.
Andrej Czán, Ondrej Kubala, Igor Danis, Tatiana Czánová, Jozef Holubják and Matej Mikloš
, A. A.: Multilayer composite nanoscale coatings as a method to increase reliability and tool life of cutting tools made of mixed ceramic Al 2 O 3 -TiC, In Mechanics&Industry, Vol. 17. No. 7, 2016, ISSN: 2257-7777
 Czan, A., Sajgalik, M., Martikan, A., Mrazik, J.: Observation Of Dynamic Processes In Cutting Zone When Machining NickelAlloys. In Communications – Scientific Letters of the University of Zilina, vol. 16, No. 3A, 161-168, 2014, ISSN 1335-4205
 Stančeková, D., Pilc, J., Struhárňanský, J., Janota, M., Varga, D.: Study of the Wear of the
In this document I am describing milling possibilities of nickel alloy Inconel 718. In the beginning is described use of nickel alloys in industry and division of nickel alloys. Further is described nickel alloy what I used - Inconel 718, on this material I make all my tests of machi-nability. Further chapters describe recommended cutting materials for nickel alloys milling. Cutters with exchan-geable sintered carbide blade plates were used as cutting tools company Pramet Tools s.r.o. Main goal was inve-stigate durability and wear of indexable cutting inserts for different cutting procedures. It was mainly about different combinations of used cutting speeds and feeds. The final part includes a summary of the results. The results are ones from first steps to definition of effective nickel alloy machining.
Kobaltové a niklové slitiny jsou běžně používaným materiálem v zubním lékařství. Jedním z důvodů použití je snaha o nahrazení slitin drahých kovů, jejichž cena neustále vzrůstá. Slitiny navíc v porovnání se zlatem a jeho slitinami dosahují vyšších modulů pružnosti, což umožňuje zmenšení hmotnosti dentálních prací při zachování stejných pevnostních charakteristik. Práce byla zaměřena na studium korozního chování komerčně dostupných slitin niklu a kobaltu užívaných v bioaplikacích. Byla studována náchylnost k nerovnoměrným formám koroze a posouzen vliv mikrostruktury na charakter korozního napadení. Korozní chování slitin bylo hodnoceno v modelových tělních tekutinách s použitím elektrochemických technik. Materiály s výjimkou niklové slitiny s obsahem ceru vykazovaly dobrou korozní odolnost při potenciálech odpovídajících oxidačně redukčním potenciálům prostředí lidského organizmu. Výrazná korozní aktivita niklové slitiny s obsahem ceru byla dána přítomností neušlechtilé fáze bohaté na cer. Bylo prokázáno, že mikrostrukturní heterogenita studovaných materiálů má vliv na korozní chování.
Within the national and international research program of materials for advanced nuclear reactors Czech organizations contributed with several tests of metallic alloys. The specimens of the alloys were first exposed in the long term (up to 1500 hours) in simulated advanced gas cooled reactor coolant environment at 750-900 °C. After exposure the degradation of tested materials was explored, especially changes in material microstructure, corrosion damage and corrosion layer composition and in some cases also changes in mechanical properties were observed. In this paper selected results of exposure tests in high temperature helium of alloy 800 H, austenitic steel 316L and high-temperature nickel alloys are presented.
Modern design solutions of power boiler using the welded fin tubes for heat exchangers. Depending on thermal parameters (pressure and temperature), the heat transfer fluid and flue gas these constructions can be preheater, economizers or superheaters. Their use can significantly increase the energy efficiency of boilers. For the manufacture of welded fin tubes are used non-alloy steels and low-alloy C-Mo, C-Cr-Mo. Analysis of project assumptions supercritical blocks indicates that the range of conventional steel for power and martensitic steels has been depleted. Designing higher performance outlet of steam to 720°C and 35MPa requires the use of austenitic steels and nickel alloys. These materials are not easily available and not fully recognized, both technologically and in terms of materials, especially in the area of their weldability. In this work, performed the review of probably directions of development of materials for the finned tubes, with a particular focus on laser welding technology.
J. Poláčková, J. Petrů, M. Janák, J. Berka and A. Krausová
Carbon Capture and Storage (CCS) technologies are a perspective solution to reduce the amount of CO2 emissions. One of promising methods is Ca-looping, which is based on carbonation and calcination reactions. During both of these processes, especially calcination, high temperatures (650-950°C) are required. This means high demands on the corrosion resistance of equipment materials. Therefore, we carried out a study to suggest materials with suitable properties for calciner construction, which have to be particularly heat resistant: stainless steels (AISI 304, AISI 316L and AISI 316Ti) and nickel alloys (Inconel 713, Inconel 738, Incoloy 800H). A special device simulating calciner environment was built for this purpose. Chosen materials were tested in temperature 900°C, atmospheric pressure and gaseous environment with composition that can be possible in a calciner. The surfaces of materials were evaluated to determine composition and properties of formed oxide layers. High temperature oxidation was observed on all tested materials and oxide exfoliation occurred on some of tested materials (304, 316L).