Successive Grinding and Polishing Effect on the Retained Austenite in the Surface of 42CrMo4 Steel

Low-alloy 42CrMo4 steels were studied by 57Fe Mössbauer spectroscopy (MS), X-ray diffractometry (XRD), and Energy Dispersive X-ray Spectroscopy (EDS) measurements. The investigations were performed on metallographic samples, which were subjected to a series of successive grinding and polishing with a progressively finer grit. Conversion X-ray Mössbauer spectroscopy (CXMS) was used to determine the occurrence of austenite in steel samples. It is a unique method detecting the austenite content very sensitively. Six samples with different surface preparation were investigated, starting with 4.8% of austenite on an as-cut sample, and a large decrease in the retained austenite to 2.6% was observed after the first grinding of a hardened cut sample. Additionally, an unexpectedly large decrease in the austenite content to 2.3% was found due to the final polishing. A second time applied successive grinding and polishing of all samples resulted in identical austenite content determined by CXMS of approx. 5%, which proved the applicability of the CXMS method. Generally, the result calls attention to the importance of preparation of metallurgical samples by grinding and polishing where the results can vary significantly on the level of surface processing.

One-step fabrication of soft calcium superhydrophobic surfaces by a simple electrodeposition process

We investigated a one-step method for calcium superhydrophobic surface preparation and researched the formation process of loose, flower-like microstructures. Also, we found that the pressing force strongly impacts the dynamics of water droplets.

Evaluation of the Effect of Cold Plasma Treatment on the Microshear Bond Strength of Composite Resin Restorations to Dentin using Different Adhesive Systems and the Effect of Thermocycling

Introduction: Currently, non-thermal plasma is used to modify the enamel and dentin surfaces to improve the bonding surface to dental composite resins. Non-thermal plasma creates a hydrophilic surface, decreases the contact angle, and improves the bonding quality. The present study aimed to evaluate the microshear bond strength (µSBS) of composite resins to dentin using different adhesive systems. Materials and Methods: Bovine incisor teeth were randomly assigned to three groups of G-Premio, Clearfil SE Bond, and Adper Single Bond adhesive groups after preparation. Each group was divided into two subgroups in terms of argon plasma surface preparation, and each subgroup was divided into two groups in terms of thermocycling (n=12). The microshear bond strength of the samples was determined using a universal testing machine. Three-way ANOVA was used to analyze the effect of the adhesive, plasma preparation, and thermocycling. Post hoc Tukey tests were used for two-by-two comparisons of µSBS. Statistical significance was set at P <0.05. Results: The results of the µSBS test showed that the application of plasma resulted in a significant increase in the mean µSBS in the G-Premio group, with no significant increase in the Clearfil SE bond and Adper Single groups. The effect of thermocycling after plasma application was significant only in the Adper Single group. Conclusion: The application of plasma might increase the bond strength of composite resins to dentin. However, further studies are necessary.

Effect of Spontaneous and Water-Based Passivation on Components and Parameters of Ti6Al4V (ELI Grade) Surface Tension and Its Wettability by an Aqueous Solution of Sucrose Ester Surfactants

Solid wettability is especially important for biomaterials and implants in the context of microbial adhesion to their surfaces. This adhesion can be inhibited by changes in biomaterial surface roughness and/or its hydrophilic–hydrophobic balance. The surface hydrophilic–hydrophobic balance can be changed by the specifics of the surface treatment (proper conditions of surface preparation) or adsorption of different substances. From the practical point of view, in systems that include biomaterials and implants, the adsorption of compounds characterized by bacteriostatic or bactericidal properties is especially desirable. Substances that are able to change the surface properties of a given solid as a result of their adsorption and possess at least bacteriostatic properties include sucrose ester surfactants. Thus, in our studies the analysis of a specific surface treatment effect (proper passivation conditions) on a biomaterial alloy’s (Ti6Al4V ELI, Grade 23) properties was performed based on measurements of the contact angles of water, formamide and diiodomethane. In addition, the changes in the studied solid surface’s properties resulting from the sucrose monodecanoate (SMD) and sucrose monolaurate (SML) molecules’ adsorption at the solid–water interface were also analyzed. For the analysis, the values of the contact angles of aqueous solutions of SMD and SML were measured at 293 K, and the surface tensions of the aqueous solutions of studied surfactants measured earlier were tested. From the above-mentioned tests, it was found that water environment significantly influences the components and parameters of Ti6Al4V ELI’s surface tension. It also occurred that the addition of both SMD and SML to water (separately) caused a drop in the water contact angle on Ti6Al4V ELI’s surface. However, the sucrose monolaurate surfactant is characterized by a slightly better tendency towards adsorption at the solid–water interface in the studied system compared to sucrose monodecanoate. Additionally, based on the components and parameters of Ti6Al4V ELI’s surface tension calculated from the proper values of components and parameters of model liquids, it was possible to predict the wettability of Ti6Al4V ELI using the aqueous solutions of SMD and SML at various concentrations in the solution.

Influence of Surface Preparation on Cracking Phenomena in TIG-Welded High and Medium Entropy Alloys

Multi-element systems with defined entropy (HEA—high entropy alloy or MEA—medium entropy alloy) are rather new material concepts that are becoming increasingly important in materials research and development. Some HEA systems show significantly improved properties or combinations of properties, e.g., the overcoming of the trade-off between high strength and ductility. Thus, the synthesis, the resulting microstructures, and properties of HEA have been primarily investigated so far. In addition, processing is crucial to achieve a transfer of potential HEA/MEA materials to real applications, e.g., highly stressed components. Since fusion welding is the most important joining process for metals, it is of vital importance to investigate the weldability of these materials. However, this has rarely been the subject of research to date. For that reason, in this work, the weldability depending on the surface preparation of a CoCrFeMnNi HEA and a CoCrNi MEA for TIG welding is investigated. The fusion welding of longer plates is described here for the first time for the CoCrNi alloy. The welds of both materials showed distinct formation of cracks in the heat affected zone (HAZ). Optical and scanning electron microscopy analysis clearly confirmed an intergranular fracture topography. However, based on the results, the crack mechanism cannot be conclusively identified as either a liquid metal embrittlement (LME) or hot cracking-like liquid film separation.

Influence of Sandblasting and Chemical Etching on Titanium 99.2–Dental Porcelain Bond Strength

The metal–ceramic interface requires proper surface preparation of both metal and ceramic substrates. This process is complicated by the differences in chemical bonds and physicochemical properties that characterise the two materials. However, adequate bond strength at the interface and phase composition of the titanium-bioceramics system is essential for the durability of dental implants and improving the substrates’ functional properties. In this paper, the authors present the results of a study determining the effect of mechanical and chemical surface treatment (sandblasting and etching) on the strength and quality of the titanium-low-fusing dental porcelain bond. To evaluate the strength of the metal-ceramic interface, the authors performed mechanical tests (three-point bending) according to EN ISO 9693 standard, microscopic observations (SEM-EDS), and Raman spectroscopy studies. The results showed that depending on the chemical etching medium used, different bond strength values and failure mechanisms of the metal-ceramic system were observed. The analyzed samples met the requirements of EN ISO 9693 for metal-ceramic systems and received strength values above 25 MPa. Higher joint strength was obtained for the samples after sandblasting and chemical etching compared to the samples subjected only to sandblasting.

THE CHALLENGES OF MAJOR TANK COATING REFURBISHMENT PROJECTS FOR ON-STATION FLOATING ASSETS

The objective of this paper is to acknowledge that major tank coating refurbishment projects to FPSO’s and FSU’s are likely to be required during the life of these assets. It highlights the key challenges of achieving these major coating projects in an offshore environment, whilst the assets remain operational and in-production. As these floating assets age the original coatings applied to protect the internal (and external) hull, deteriorate. In an industry with a reluctance for extensive dry-dockings, there is an expectation that any coating refurbishment campaigns can be achieved safely and efficiently whilst the assets remain on-station and in-production, in preference to costly steel renewal’s which may be required at a future date if coatings are not maintained in good condition. With often complex, congested and hazardous topsides processing equipment and pipework directly above the hull tanks, there’s a need for systems, procedures, and specialist equipment to ensure the safety of the personnel entering confined spaces for extended periods. There’s also a need to plan and engineer the works appropriately, using best practice and emergent technologies to improve safety, reduce bedding impacts and to ensure the success of the coating campaign. This paper explores the challenges of major coating projects by discussing the importance of planning and preparation, the need to create a safe working environment within the confined space worksites, the role surface preparation plays in the success of coating projects, and finally the application of coatings and the challenges this operation can present. The key considerations are summarised in 10 specific conclusions as guidance to promote successful project outcomes.

Повышение надежности антикоррозионных покрытий для защиты объектов магистральных нефтепроводов с использованием механизма управления качеством

The problem of improving the quality of anticorrosive coatings used at hazardous production facilities, including main oil and oil-products pipelines, is relevant both for pipeline system operators and for manufacturers of materials and equipment. Its solution is facilitated, among other things, by the improvement of the compliance evaluation system for this type of product, which is the subject of consideration by the authors of this article. The purpose of the article is to analyze the compliance evaluation system of anticorrosive coatings used at the facilities of main pipelines operated by the entities of the Transneft system. As part of the paper, the main criteria for evaluation of the compliance of anticorrosive coatings used to protect the surface of tanks, pipelines, structures and equipment of aboveground arrangement are analyzed. The main requirements of national, international and industry standards for environmental conditions and surface preparation for anticorrosion treatment, the quality of the cured coating are considered. An integrated approach to the compliance evaluation of anticorrosive coatings is presented, which makes it possible to improve the quality control of this type of product throughout the product life cycle. Проблема повышения качества антикоррозионных покрытий, применяемых на опасных производственных объектах, в том числе магистральных нефте- и нефтепродуктопроводах, актуальна как для операторов трубопроводных систем, так и для производителей материалов и оборудования. Ее решению способствует в том числе совершенствование системы оценки соответствия данного вида продукции, что является предметом рассмотрения авторов настоящей статьи. Цель статьи – анализ системы оценки соответствия антикоррозионных покрытий, используемых на объектах магистральных трубопроводов, эксплуатируемых организациями системы «Транснефть». В рамках работы проанализированы основные критерии оценки соответствия антикоррозионных покрытий, применяемых для защиты поверхности резервуаров, трубопроводов, конструкций и оборудования надземного исполнения. Рассмотрены основные требования национальных, международных и отраслевых стандартов к условиям окружающей среды и подготовке поверхности к антикоррозионной обработке, качеству отвержденного покрытия. Представлен комплексный подход к оценке соответствия антикорозионных покрытий, позволяющий усовершенствовать контроль качества данного вида продукции на всех стадиях жизненного цикла.