Metallurgical Tests in Endodontics: A Narrative Review

Since there are no reviews of the literature on this theme, the aim of this narrative review is to summarize the metallurgical tests used in endodontics, pointing out their functional use and their pros and cons and giving readers a user-friendly guide to serve as an orientation aid in the plethora of metallurgical tests. With this purpose, a literature search for articles published between January 2001 and December 2021 was conducted, using the electronic database PubMed to collect all published articles regarding the metallurgical tests used in endodontics for the evaluation of NiTi rotary instruments. The search was conducted using the following keywords: “metallurgy”, “differential scanning calorimetry” (DSC), “X-ray diffraction” (XRD), “atomic force microscopy” (AFM), “energy-dispersive X-ray spectroscopy” (EDS), “focused ion beam analysis” (FIB) and “Auger electron spectroscopy” (AES) combined with the term “endodontics” or “NiTi rotary instruments”. Considering the inclusion and exclusion criteria, of the 248 articles found, only 81 were included in the narrative review. According to the results, more than 50% of the selected articles were published in one of the two most relevant journals in endodontics: International Endodontic Journal (22.2%) and Journal of Endodontics (29.6%). The most popular metallurgical test was DSC, with 43 related articles, followed by EDS (33 articles), AFM (22 articles) and XRD (21 articles). Few studies were conducted using other tests such as FIB (2 articles), micro-Raman spectroscopy (4 articles), metallographic analysis (7 articles) and Auger electron spectroscopy (2 articles).

Determination of the Causes of Copper Wires Beads after Fire in Vehicles

An electrical installation that simulates an automobile DC power supply system with a voltage of 12 V has been created. An experimental simulation of a short circuit at currents up to 400 A on copper multi-wire and single-wire conductors under normal environmental conditions is carried out. The copper wires beads were annealed in a furnace at temperatures from 700 to 1000 °C for 20, 40 and 60 minutes. Metallographic analysis of copper wires beads was carried out. The temperatures and times that of at which the signs of short circuit and overcurrent are destroyed has been revealed. Obtained results contribute to improvement evidence’s researching in the fire investigation of motor vehicles electrical wiring after a fire. Keywords: Arc beads, Copper, Metallographic analysis, Electrical Short Circuit, Wires.

Current state of steelmaking slag processing

In the present work, the properties and composition of steelmaking slag are assessed by analysing existing processing methods, including desulfurisation and dephosphorisation. The atomic absorption and optical emission methods were used to study the chemical composition of slag samples, and metallographic analysis was used to study their microstructure. Major approaches to processing slags applied in Russia and abroad were studied. It was shown that steelmaking slags are neutralised and treated by various methods and subsequently applied in construction and road industries, while the obtained phosphorus-containing products are used in agriculture instead of superphosphate. In addition, these products reduce lime consumption and improve slag formation in steelmaking. The key factor hampering reusing electric steelmaking and converter slags for metal refining is shown to be the presence of phosphorus. The chemical composition of slag samples from the electric steelmaking production was analysed; the iron content amounted to 33.2 wt%, calcium – 19.15 wt%, phosphorus – 0.33 wt% and silicon – 5.39 wt%. Iron is present in the oxidised form (FeO, Fe2O3 and Fe3O4), silicon and calcium in the form of dicalcium silicate (2CaO ∙ SiO2 ), phosphorus in the form of calcium silicophosphate having complex composition – Ca2(SiO4)6(Ca3(PO4)2. Phosphorus is fed to the melting units with gangue minerals, agglomerate, ore and fluxes. When the slags are reused, phosphorus returns to the metal, thus contaminating the final product. Possible methods for extracting phosphorus from steelmaking slags include magnetic and electrostatic separation, gravity and flotation concentration, as well as hydrometallurgical processing.

Effects of Welding Wire Composition on Microstructure and Mechanical Properties of Welded Joint in Al-Mg-Si Alloy

The effects of welding wire composition on microstructure and mechanical properties of welded joint in Al-Mg-Si alloy were studied by electrochemical test, X-ray diffraction (XRD) analysis and metallographic analysis. The results show that the weld zone is composed of coarse columnar dendrites and fine equated grains. Recrystallized grains are observed in the fusion zone, and the microstructure in the heat affected zone is coarsened by welding heat. The hardness curve of welded joint is like W-shaped, the highest hardness point appears near the fusion zone, and the lowest hardness point is in the heat affected zone. The main second phases of welded joints are: matrix α-Al, Mg2Si, AlMnSi, elemental Si and SiO2. The addition of rare earth in welding wire can refine the grain in weld zone obviously, produce fine grain strengthening effect, and improve the electrochemical performance of weld.

Hot Deformation Behavior of PM Ni with Harmonic Microstructure

The hot deformation behavior of a harmonic-structured pure nickel has been studied and compared with the hot deformability of a homogeneously structured nickel. Both materials were produced via the powder metallurgy route through the Spark Plasma Sintering (SPS) of mechanical milled and un-milled powders. Hot deformation was evaluated through compression tests at three different temperatures (400 °C, 800 °C, and 1300 °C), covering a wide range in the homologous temperature spectrum for Ni (from 0.39 to 0.91), and at three different strain rates (0.001, 0.01, and 0.1 s−1). The evaluation of the stress–strain curves showed a higher hot compression resistance for the harmonic-structured nickel, together with higher strain hardening and strain rate sensitivity, thanks to the peculiar microstructural features of this material. Through the metallographic analysis of the specimens after hot compression, different mechanisms were identified as responsible for the deformation behavior in relation to the temperature of testing. While at 400 °C dynamic recrystallization has slightly started, at 800 °C it is widely diffused, and at 1300 °C it is replaced by grain growth and diffusion creep phenomena.

Express method for the testing of tribotechnical properties of lubricants

The paper presents the results of experimental study of the tribotechnical properties of lubricants on a unit that simulates the geometric, kinematic and force similarity of well drilling conditions. Bearings with different radial clearances and the same chemical-thermal treatment were investigated. Data registration was carried out on cathode, loop oscilloscopes and electronic recorders. The load on the bearing, the moment of rolling resistance on the journal, and the angular speed of rotation of the outer race were recorded. The temperature was registered using artificial and semiartificial thermocouples. A strobotachometer was used to determine the portable speed of the rolling bodies. The external appearance of all rolling elements was investigated, metallographic analysis of thin surface layers of all rolling elements was carried out, mathematical processing of test results was carried out. It is shown that for the express assessment of the tribotechnical properties of lubricants, the amplitude value of the oscillation of the rolling resistance moment can be used. Keywords: friction; lubrication; tribotechnical Properties; drilling.

Study of the Structural-Phase State of Pipeline Welded Metal

The issues of research of structural changes as applied to welded joints of steam pipelines are considered. The results of metallographic analysis of structural changes in the metal of steam pipelines are presented. There was carried out the analysis for a number of samples cut from different sections of the steam line at different operating time under creep and low-cycle fatigue conditions. In the analyzing process of the images of micro sections, the relative content of the structural-phase components and their distribution in the metal were revealed. A comparative analysis of the statistical characteristics of the distribution and the relative content of structural components for different sections of the metal of welded joints with different operating time is carried out. A scientifically substantiated description of structural changes in the metal of various sections of samples of welded joints is given, as well as the possibility of extending the service life of elements of steam pipelines with a degraded structure and the presence of damageability. The most promising, in the opinion of the authors, directions of further research of samples to provide conditions for extending the service life of steam pipelines have been formulated and substantiated.

Viking Age Swords from Telemark, Norway: An Integrated Technical and Archaeological Investigation

Viking Age Swords from Telemark, Norway. An Integrated Technical and Archaeological Investigation provides a metallographic analysis of 21 Viking Age swords found in the county Telemark in southeastern Norway. The book is the result of a collaboration between archaeologist Irmelin Martens and chemist Eva Elisabeth Astrup. 220 swords have been found in Telemark, and they are a mix of domestic Norwegian and imported European types. The difficulties in determining which ones were made in Norway are complicated by and closely connected to the specific skills Norwegian blacksmiths had mastered with respect to both blade construction and inlay decoration. The metallographic investigations revealed five construction types for sword blades, of which four, requiring different technical levels of smithing, may well have been mastered by Norwegian blacksmiths at that time. Combined with x-ray radiographic studies, the metallographic investigations indicate that new techniques were indeed introduced and disseminated among weaponsmiths during the Viking Age. The findings are also probably representative for the combined total of more than 3000 swords found in all areas of the country. The majority are domestic types, and their great number obviously reflects the organization of sword production and influenced blacksmiths’ social standing.

Quality assessment of AL-C-B coatings on steel surfaces obtained by electro spark alloying

Problem. As a rule, during the operation of the product, the surface layers of materials are most affected. These can be parts that work in aggressive environments, at high temperatures, various force actions, the presence of abrasive particles, etc. Under such conditions, different types of steels and alloys are used, and, most commonly, it is high-alloy, which significantly complicates the manufacturing process and increases the cost of the finished product. Diffusion coating methods are the most widespread in the industry, which is due to the best study and ease of these processes. However, there are alternative methods of surface treatment, which are devoid of the disadvantages of diffusion methods. The goal is to develop a method of obtaining boron-containing coatings of the Al-C-B system by the electro spark alloying (ESA), applying STS to the treated surface, to study the processes of structural and phase formation of surface layers depending on the energy processes of ESA and substrate material. Methology. Samples made of steel 20 and 40 were used for the study, on which a coating consisting of their sulfur ointment, aluminum powder, amorphous boron powder was applied. Without waiting for drying, the ESA surfaces of the samples were carried out with a graphite electrode on an installation with a discharge energy of 0.13, 0.55 and 4.9 J. The surface roughness after treatment was determined on a profilograph-profilometer by removing and processing profilograms. Metallographic analysis of coatings was performed using an MIM-7optical microscope, and durometric studies were made on the PMT-3 device according to standard methods. Results: the article presents the original method for obtaining boron-containing coatings of the Al-C-B system by the ESA method, which involves applying a coating consisting of sulfur ointment, aluminum powder, amorphous boron powder on the treated surface, followed by electric spark doping with a graphite electrode.

Features of damage to welded joints of steam pipes made of steel 12X1M1F and 15X1MF

A significant number of heat and power equipment, including welded connections of steam pipelines made of 15x1m1f and 12x1mf Steels, have now reached the design service life. Their practical experience is about 200,000 hours at an estimated temperature of 545°C, and the park resource according to regulatory documentation is 250,000 hours. Note that aging welded joints are operated in conditions of start-ups and stops, which have become more frequent, which contributes to an increase in the intensity of their damage. In this connection, the question arose about the possibility of their operation longer than the estimated period in the new conditions. Goal. The goal is study of the features of damage to welded elements of steam pipelines operating in conditions of creep and low cycle fatigue. Methodology. The study of samples from existing damaged steam pipelines was carried out by the method of structural analysis, based on the consideration of the processes of structural and phase changes occurring in the areas of welded joints and conclusions were drawn regarding their resistance to destruction during operation. Results. The mechanisms of crack formation, their causes and the main provisions of metallographic analysis on the study of damaged welded joints operating under creep conditions and representing a certain number of types of cracks are presented. Such cracks are cold-breaking cracks, which are brittle cracks at moderate temperatures (up to 100–150 0C) during hydraulic tests and start-ups; long-term ductility failure cracks, which are brittle cracks caused by the failure of long-term ductility creep temperatures and rated stresses below permissible; cracks on exhausted areas, which are cracks when operating in the range of creep temperatures and rated stresses above permissible and fatigue cracks, which are cracks caused by the action of variable stresses with an amplitude greater than permissible values. Scientific novelty and practical significance. It is established that the mechanism of aging of long-term operated welded joints of steam pipelines is associated with structural transformations that cause the appearance of cracks in the welded joints.