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This work focuses on gaseous reactive flows in ideal and non-ideal reactors. The objective of this research is the development of models for the numerical simulation of homogeneous reactive flows under vacuum carburizing conditions of steel with propane and acetylene. These models can be used for further investigations of heterogeneous reactions during vacuum carburizing of steel to predict the carbon flux on the complex shaped steel parts to understand and, eventually, optimize the behavior of the whole reactor.arburizing is the case-hardening process in which carbon is added to the surface of low-carbon steels at temperatures generally between 850 and 1050 °C. In the conventional gas carburizing at atmospheric pressure, the carbon potential is controlled by adjusting the flow rate of the carburizing gas. Carbon potential of the furnace atmosphere can be related to partial pressure of CO2 or O2 or vapour pressure of water by equilibrium relationships and a sensor can be used to measure it. This method of carbon-potential control cannot be used for vacuum gas carburizing due to the absence of thermodynamic equilibrium which is one of the main difficulties of the vacuum carburizing process. The formation of soot during carburization isalso undesirable and the process parameters should be selected such that the formation of soot is minimized. The amount of carbon available for carburizing the steel depends on the partial pressure of the carburizing gas, carbon content in the carburizing gas and the pyrolysis reactions of the carburizing gas. The pyrolysis reactions of the carburizing gas are also affected by the contacting pattern or how the gas flows through and contacts with the steel parts being carburized. This work focuses on gaseous reactive flows in ideal and non-ideal reactors. The objective of this research is the development of models for the numerical simulation of homogeneous reactive flows under vacuum carburizing conditions of steel with ropane and acetylene. These models can be used for further investigations of heterogeneous reactions during vacuum carburizing of steel to predict the carbon flux on the complex shaped steel parts to understand and, eventually, optimize the behavior of the whole reactor. Two different approaches have been used to model the pyrolysis of propane and acetylene under vacuum carburizing conditions of steel. One approach is based on formal or global kinetic mechanisms together with the computational fluid dynamics (CFD) tool. The other approach is based on detailed chemistry with simplified or ideal flow models. Two global mechanisms developed at the Engler-Bunte-Institut for pyrolysis of propane and acetylene respectively were used in this work. One detailed mechanism developed at the Institute of Chemical Technology by the research group of Professor Deutschmann was used for modeling the pyrolysis of both the propane and acetylene. Experimental data from investigations on vacuum carburizing conducted at the Engler-Bunte-Institut were used to validate the modeling results.

carburizing --- gaseous reactive flows

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Roller bearings. --- Residual stress. --- Steels. --- Hardness. --- Carburizing. --- Compression loads. --- Corrosion resistance. --- Lubrication.

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Steels and their heat treatment are still very important in modern industry because most industrial components are made from these materials. The proper choice of steel grades along with their suitable processing makes it possible to reduce the weight of the components, which is closely related to energy and fuel savings. This has decisive importance in branches such as the automotive, transport, consumer industries. A great number of novel heat- and surface-treatment techniques have been developed over the past three decades. These techniques involve, for example, vacuum treatment, sub-zero treatment, laser/electron beam surface hardening and alloying, low-pressure carburizing and nitriding, and physical vapour deposition. This Special Issue contains a collection of original research articles on not only advanced heat-treatment techniques—carburizing and sub-zero treatments—but also on the microstructure–property relationships in different ferrous alloys.

History of engineering & technology --- Vanadis 6 die steel --- surface finish --- nitriding --- PVD coating --- toughness --- fractography --- cryogenic treatment --- cryo-treatment --- mechanical properties --- microstructure --- cryo-processing --- 20Cr2Ni4A --- vacuum carburizing --- ion implantation --- rare earths --- catalysis --- carbon diffusion --- vanadis 6 steel --- sub-zero treatment at −75 °C --- hardness --- fracture toughness --- grade 92 steel weldment --- post-welding heat treatment --- tensile straining --- hydrogen embrittlement --- metallography and fractography --- ledeburitic tool steels --- carburizing --- rare-earth element pre-implantation --- sub-zero treatments

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The innovative coating and surface hardening technologies developed in recent years allow us to obtain practically any physical–mechanical or crystal–chemical complex properties of the metalworking tool surface layer. Today, the scientific approach to improving the operational characteristics of the tool surface layers produced from traditional tools industrial materials is a highly costly and long-lasting process. Different technological techniques, such as coatings (physical and chemical methods), surface hardening and alloying (chemical-thermal treatment, implantation), a combination of the listed methods, and other solutions are used for this. This edition aims to provide a review of the current state of the research and developments in the field of coatings and surface hardening technologies for cutting and die tools that can ensure a substantial increase of the work resource and reliability of the tool, an increase in productivity of machining, accuracy, and quality of the machined products, reduction in the material capacity of the production, and other important manufacturing factors. In doing so, the main emphasis should be on the results of the engineering works that have had a prosperous approbation in a laboratory or real manufacturing conditions.

Technology: general issues --- hierarchical structure --- multilayer PVD coating --- stochastic process --- convection and diffusion --- reactive magnetron sputtering --- argon --- nitrogen and ethylene --- TaSi2 --- Ta3B4 and ZrB2 --- SHS and hot pressing --- composition and structure --- hardness and elastic modulus --- friction coefficient and wear resistance --- oxidation resistance --- diamond-like coatings --- nitride sublayer --- index of plasticity --- adhesive bond strength --- end mills --- hard alloy --- wear resistance --- milling of aluminum alloys --- milling of structural steels --- surface quality --- modeling --- carbon flux --- low-pressure vacuum carburizing --- medium-high alloy steel --- nanolayered PVD coating --- microdroplets --- crack formation --- tool wear --- nanolayered coating --- microparticles --- monocrystalline --- high-pressure, high-temperature (HPHT) diamond --- chemical vapor deposition (CVD) diamond --- high-fluence ion irradiation --- Ar+ --- C+ --- SEM --- AFM --- Raman spectra --- electrical conductivity --- AlCr-based --- CrAl-based --- (AlCrX)N --- (Al1−xCrx)2O3 --- arc --- HiPIMS --- nanolayers --- nanocomposite --- structure --- properties --- roughness --- coatings --- finish turning --- PCBN --- tempered steel --- micro cutters --- cutting edges --- wear-resistance --- coating deposition --- adhesion --- plasma --- ions --- charge exchange collisions --- fast gas atoms --- etching --- sharpening --- diamond-like carbon coating --- high-speed milling --- nickel alloy --- SiAlON --- spark plasma sintering --- adaptive coating --- adaptive material --- composite powder HSS --- cutting tool --- secondary structures --- surface layer --- thermal-force loads --- hierarchical structure --- multilayer PVD coating --- stochastic process --- convection and diffusion --- reactive magnetron sputtering --- argon --- nitrogen and ethylene --- TaSi2 --- Ta3B4 and ZrB2 --- SHS and hot pressing --- composition and structure --- hardness and elastic modulus --- friction coefficient and wear resistance --- oxidation resistance --- diamond-like coatings --- nitride sublayer --- index of plasticity --- adhesive bond strength --- end mills --- hard alloy --- wear resistance --- milling of aluminum alloys --- milling of structural steels --- surface quality --- modeling --- carbon flux --- low-pressure vacuum carburizing --- medium-high alloy steel --- nanolayered PVD coating --- microdroplets --- crack formation --- tool wear --- nanolayered coating --- microparticles --- monocrystalline --- high-pressure, high-temperature (HPHT) diamond --- chemical vapor deposition (CVD) diamond --- high-fluence ion irradiation --- Ar+ --- C+ --- SEM --- AFM --- Raman spectra --- electrical conductivity --- AlCr-based --- CrAl-based --- (AlCrX)N --- (Al1−xCrx)2O3 --- arc --- HiPIMS --- nanolayers --- nanocomposite --- structure --- properties --- roughness --- coatings --- finish turning --- PCBN --- tempered steel --- micro cutters --- cutting edges --- wear-resistance --- coating deposition --- adhesion --- plasma --- ions --- charge exchange collisions --- fast gas atoms --- etching --- sharpening --- diamond-like carbon coating --- high-speed milling --- nickel alloy --- SiAlON --- spark plasma sintering --- adaptive coating --- adaptive material --- composite powder HSS --- cutting tool --- secondary structures --- surface layer --- thermal-force loads

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The innovative coating and surface hardening technologies developed in recent years allow us to obtain practically any physical–mechanical or crystal–chemical complex properties of the metalworking tool surface layer. Today, the scientific approach to improving the operational characteristics of the tool surface layers produced from traditional tools industrial materials is a highly costly and long-lasting process. Different technological techniques, such as coatings (physical and chemical methods), surface hardening and alloying (chemical-thermal treatment, implantation), a combination of the listed methods, and other solutions are used for this. This edition aims to provide a review of the current state of the research and developments in the field of coatings and surface hardening technologies for cutting and die tools that can ensure a substantial increase of the work resource and reliability of the tool, an increase in productivity of machining, accuracy, and quality of the machined products, reduction in the material capacity of the production, and other important manufacturing factors. In doing so, the main emphasis should be on the results of the engineering works that have had a prosperous approbation in a laboratory or real manufacturing conditions.

hierarchical structure --- multilayer PVD coating --- stochastic process --- convection and diffusion --- reactive magnetron sputtering --- argon --- nitrogen and ethylene --- TaSi2 --- Ta3B4 and ZrB2 --- SHS and hot pressing --- composition and structure --- hardness and elastic modulus --- friction coefficient and wear resistance --- oxidation resistance --- diamond-like coatings --- nitride sublayer --- index of plasticity --- adhesive bond strength --- end mills --- hard alloy --- wear resistance --- milling of aluminum alloys --- milling of structural steels --- surface quality --- modeling --- carbon flux --- low-pressure vacuum carburizing --- medium-high alloy steel --- nanolayered PVD coating --- microdroplets --- crack formation --- tool wear --- nanolayered coating --- microparticles --- monocrystalline --- high-pressure, high-temperature (HPHT) diamond --- chemical vapor deposition (CVD) diamond --- high-fluence ion irradiation --- Ar+ --- C+ --- SEM --- AFM --- Raman spectra --- electrical conductivity --- AlCr-based --- CrAl-based --- (AlCrX)N --- (Al1−xCrx)2O3 --- arc --- HiPIMS --- nanolayers --- nanocomposite --- structure --- properties --- roughness --- coatings --- finish turning --- PCBN --- tempered steel --- micro cutters --- cutting edges --- wear-resistance --- coating deposition --- adhesion --- plasma --- ions --- charge exchange collisions --- fast gas atoms --- etching --- sharpening --- diamond-like carbon coating --- high-speed milling --- nickel alloy --- SiAlON --- spark plasma sintering --- adaptive coating --- adaptive material --- composite powder HSS --- cutting tool --- secondary structures --- surface layer --- thermal-force loads