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In thermal and nuclear power plants, numerous corrosion phenomena observed in copper alloy condenser tube nests have been identified by means of metallography. Particular importance has been given in the paper to verification of secondary dezincification, initiated at the boundaries of the α‐grains in copper tubes. Typical phenomena of corrosion under stress and of erosion‐corrosion have been observed in other copper alloy tube nests, with circulation of sea and river water. In some instances a semi‐quantitative check of the phenomenon on the whole tube nest, by means of eddy currents, has been made possible through the simultaneous application of metallographic analysis.

The purpose of this paper is to assess the technical state of old and repair steels of Shukhov’s tower elements after operation during ~ 110 and 70 years of the water tower in Nikolaev, basing on their mechanical tests, metallography and fractography investigations.

For their certification, the fractographic and structural features and mechanical properties (hardness, strength, plasticity and impact toughness) were analyzed. Both the steels under consideration were characterized by low values of hardness and brittle fracture resistance. The mechanical characteristics of the old steel are lower compared with the repair one. It cannot be only explained by the quality of metal rolling. Moreover, the plasticity characteristics of both steels, defined in synthetic acid rain environment, are lower than in the air. Using fractography investigation, the operational damages in the bulk metal in the form of the elements of cleavage fracture in the central part of the fracture surfaces of specimens tested at the hydrogenation condition by synthetic acid rain environment were revealed.

The results of this study suggested a degradation of steels’ characteristics caused by the development of scattering damages during their operation. Higher relative elongation of the old steel at lower hardness and impact toughness were also evidenced in that. The metallography and fractography investigations also supported this finding.

This original study aimed at characterizing the microstructural and mechanical degradation of mild steels that was collected from Shukhov’s tower structural elements.

This paper presents the results of mean unit weight of chips and their time to ignition measured on a test stand specially designed for this purpose. In addition, the temperature of chips in the cutting area and the morphology of chips produced in HSM milling (as a temperature indicator in the cutting area) are investigated. Also, different fractions of chips produced in the dry milling of Mg alloys AZ31 and AZ91HP by a PCD end mill are examined. Finally, the paper presents conclusions and recommendations with regard to safety and efficiency of dry milling processes for the aforementioned magnesium alloys.

Milling can be used as a finishing operation, particularly when using PCD end mills. The application of this mill type isparticularly important when producing different machine and device components, especially in the aircraft industry. What can occur in dry machining operations is self-ignition. It is therefore justified to investigate chip temperature in the cutting zone, to classify produced chip fractions and to determine their mass. Safe ranges of technological parameters can be additionally determined based on metallographic analysis of chip edge partial-melting.

The experimental results helped determine the effect of technological parameters of milling on chip temperature in the cutting zone, chip mass and fragmentation and chip morphology images.

The results reported in this work are innovative in both cognitive and practical aspect. The authors are convinced that this work can contribute to overcoming the mistrust of industrial practitioners toward dry milling of Mg alloys, and also with respect to the application of relatively higher cutting speeds in dry milling of these alloys than it is common practice in industry today. The study investigates the problem of safety in dry milling of Mg alloys. The study was motivated by the milling process itself and the formation of broken chip, which causes a significant change in the character of heat transfer.

The paper presents a method for multi-criteria safety assessment in dry milling operations. Safe and effective parameter ranges are defined with respect to chip temperature in the cutting zone, fraction number and chip mass.

This paper aims to describe and document the application of commonly utilized solder joint failure analysis techniques to lead‐free solder joints.

Traditional failure analysis techniques, including visual inspection, X‐ray radiography, mechanical strength testing, dye and pry, metallography, microscopy and photomicrography, are reviewed. These techniques are demonstrated as applied to lead‐free and tin lead solder joints. Common failure modes observed in lead‐free and tin lead solder joints are described and compared.

It is shown that the traditional failure analysis techniques previously utilized for tin lead solder joints are widely applicable to the analysis of lead‐free solder joints. The changes required to effectively apply these techniques to the analysis of lead‐free solder joints are described.

This paper will be instrumental to the process, quality, reliability and failure analysis engineering disciplines in furthering understanding of the application of failure analysis techniques of both tin lead and lead‐free solder joints.

Thermal barrier coatings (TBCs) are widely used in gas turbine engines because they allow higher operating temperatures due to their thermal insulation effect. The aim of this paper is to explain the effect of the substrate (base metal) on the performance of TBCs applied to various nickel‐based superalloys and stainless steels.

Specimens were prepared by applying atmospheric plasma spraying (APS). Six TBC‐coated samples were prepared. Three of the substrates were stainless steel and the rest were nickel‐based superalloys. Characterization effort included thermal exposure, microhardness testing, optical metallography and image analysis.

Microhardness test results showed that extended periods in high‐temperature environments affected the coating morphology, which was measured by changes in the microhardness values. At the end of the long periods in the furnace, microhardness values increased, which might be a sign that modulus of the coating increased. These changes in the microhardness might be due to the sintering effect and morphological changes that occurred in the coating. Effects of thermal exposure to the coatings were also visible in the micrographs in the form of fully open cracks. Development of larger cracks was life‐threatening for the ceramic coating.

It was shown for the first time that, in the above‐mentioned crack growth and spallation stages, stainless steel and superalloy substrates showed considerably different performances. Microhardness test results of coatings on different substrates were considerably dissimilar, which was a sign that the coating morphology was affected during thermal exposure.

A key challenge found in additive manufacturing is the difficulty to produce components with replicable microstructure and mechanical performance in distinct orientations. This study aims to investigate the influence of build orientation on the fracture toughness of additively manufactured AlSi10Mg specimens.

The AlSi10Mg specimens were manufactured using the selective laser melting (SLM) technology. The fracture toughness was experimentally determined (under ASTM E399-09) using C(T) specimens manufactured in different orientations. The microstructure of the specimens was examined using metallography to determine the effects of grain orientation on fracture toughness.

The fracture toughness magnitude of manufactured specimens ranged between 36 and 50 MPam, which closely matched conventional bulk material and literature values regarding AlSi10Mg components. The C(T) specimens printed in the T-L orientation yielded the highest fracture toughness. The grain orientation and fracture toughness values confirm the anisotropic nature of SLM parts where the T-L-oriented specimen obtained the highest K_IC value. A clear interaction between the melt pool boundaries and micro-slipping during the loading application was observed.

The novelty of this paper consists in elucidating the relationship between grain orientation and fracture toughness of additively manufactured AlSi10Mg specimens because of the anisotropy generated by the different melting pool boundaries and orientations in SLM. The findings show that melt pool boundaries can behave as easier pathways for cracks to propagate and subsequently reduce the fracture toughness of specimens with cracks perpendicular to the build direction.

The paper summarises the merits and limitations of different methods used to determine the rejection criteria of the primary reformer tubes. It compares the microstructures as obtained on the outer surface of the reformer tubes with that observed in the transverse section in the regions of outer wall, midwall and inner surface. On the basis of these studies coupled with dimensional change measurements, the in situ metallographic technique has been used to monitor the condition of tubes in two reformation units and the tubes had given satisfactory service till the next turnaround as predicted.

A failed disc that was forged from S355J2 round bar was investigated in order to determine the failure route cause. The purpose of this paper is to determine the defects and route cause analysis regarding their origin.

Macroscopic evaluation, microstructure observation using light optical metallography and scanning electron microscopy with EDX analysis were the techniques used to analyse and characterize the defected areas.

Macro-inclusions (up to 850 µm) that correspond to high melting aluminium rich calcium-aluminate particles were detected. Their formation, possibly due to improper calcium treatment during ladle furnace steel refining process might be associated with clogging problems at casting. SEM-EDX analysis revealed whitish spots containing Zr that could be related to submerged entry nozzle (SEN) erosion/breakage. Characteristic is the large size and unusual shape of the traced particles, as well as the presence of low Si, Na, K. The findings indicated that nozzle clogging and/or breakage at casting was most possibly the root cause of the product’s quality degradation.

After extended root cause analysis, specific countermeasures are proposed to avoid clogging phenomena. The suggestions are based on the findings taking into account restrains of the steel-making process. Emphasis was laid in detecting the weaknesses that lead to product quality degradation and consequently in optimizing the steel-making process. Such incidents are often found during steelmaking a useful suggestion to steelmakers is to mark and remove cast parts after SEN problems are encountered. In this way quality issues in intermediate and/or final products will be avoided.

The purpose of this paper is to analyse structure and measure hardness of Co-Cr dental alloy samples made with two different technologies, conventional casting method (CCM samples) and additive direct metal laser sintering technology (DMLS samples), and to compare the results.

CCM samples were made in a conventional casting machine, using remanium 800+ Co-Cr dental alloy (Dentaurum, Ispringen, Germany). DMLS samples were fabricated out of EOS CC SP2 Co-Cr alloy (EOS, GmbH, Munich, Germany) using DMLS technology. Samples for structural analysis were plate-shaped (10 × 10 × 1.5 mm3) and for the hardness test were prismatic-shaped (55 × 10.2 × 11.2 mm3). Structure was analysed via an inverting microscope and colour metallography method.

CCM samples have a dense, irregular dendritic mesh, which is typical for the metallic phase of the Co-Cr dental alloy. DMLS alloy has a more homogenous and more compact structure, compared to CCM. Metals, the alloy basis consists of, form semilunar stratified layers, which are characteristic for the additive manufacturing (AM) technique. Hardness values of DMLS (mean value was 439.84 HV10) were found to be higher than those of CCM (mean value was 373.76 HV10).

There are several reports about possible use of AM technologies for manufacturing dental devices, and investigation of mechanical properties and biocompatibility behaviour of AM-produced dental alloys. Microstructure of Co-Cr alloy made with DMLS technology has been introduced for the first time in the present paper.

The purpose of this paper is to analyze the failure of the left waterwall tube of a boiler furnace in the steam power plant which led to cracks and rupture. Macro visual observation showed the rupture like a fish mouth with slag adhering at the outer surface of the tube. Magnetite as a protective layer was peeled off. Changes in the thickness were analyzed through dimensional measurement. In this research, an analysis to find the cause and determine the fracture mechanism is presented.

A physical analysis was performed through visual observation of changes in the thickness. Micro visual testing with a metallography test provided the data required to measure the change of grain size. The mechanical analysis used Von Mises criteria and API 530 standard and provided the pressure limits data.

The thickness of the tube decreased at the peak curvature of the tube. The smallest thickness at the peak curvature of the tube was 0.108 inches. The working pressure was 40.74 percent from permit limits with Von Mises calculations. The percentage of pressure calculated by the API standard was 48.42 percent from permit limits. Larger crystal grains occurred only in the nearby area of the oxide layer and at the end of the crack tip. It indicated that part of the inner surface had a relatively high temperature and plastic deformation occurred because of the pressure from inside the tube. Combining all these factors ruptured the tube at this location because the cross-section could not hold up the pressure.

The analysis of this discussion focuses on the combined effect of those factors causing the ability to decrease stress being received. It restricts the tube from holding up the stress and furthermore it will generate fractures.