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As a critical material for high-temperature components of aero-engines, the mechanical properties of Ti65 alloy, subjected to high-temperature and long-term thermal exposure, directly affect its service safety. The room-temperature tensile properties of the Ti65 alloy after thermal exposure to temperatures ranging from 450 °C to 650 °C for 100 h were investigated. The results indicate that as the thermal exposure temperature increases, the strength of Ti65 alloy initially increases and then decreases, while ductility exhibits a decreasing trend. The strength of the thermally exposed alloy positively correlates with the size and content of the α2 phase. The ductility of the thermally exposed alloy is comprehensively influenced by the surface oxidation behavior, α2 phase, and silicides. After the prolonged thermal exposure, stress concentration at the crack tips within the oxide layer was enhanced with the increased thickness of the surface TiO2 oxide layer, leading to premature fracture due to reduced alloy ductility. Furthermore, the α2 phase in the matrix promotes the planar slip of dislocations, while silicides at the α/β phase boundaries hinder dislocation motion, causing dislocation pile-ups. Both behaviors facilitate crack nucleation and deteriorate alloy ductility. [ABSTRACT FROM AUTHOR]

Ultra-thin 304 stainless steel can be used to flexibly display substrates after they have been subjected to chemical mechanical polishing (CMP). The thickness of the chemical oxide layer directly affects the polishing efficiency and surface quality of 304 stainless steel. In the study presented in the following paper, the thickness variation of the chemical oxide layer of 304 stainless steel was analyzed following electrochemical corrosion under different oxidant concentration conditions. Furthermore, the impact of the oxidant concentration on the grooves, chips, and scratch depth–displacement–load curves was investigated during a nano-scratching experiment. Through this process, we were able to reveal the chemical reaction mechanism between 304 stainless steel materials and oxidizers. The corrosion rate was found to be faster at 8% oxidant content. The maximum values of the scratch depth and elastic–plastic critical load were determined to be 2153 nm and 58.47 mN, respectively. [ABSTRACT FROM AUTHOR]

Developing advanced underwater welding technology for titanium, which is the key structural material for underwater applications, is of great significance for the design, fabrication, and maintenance of submarine equipment. In this study, in order to investigate the underwater welding microstructure and mechanical properties of Ti-4Al-2V alloy, underwater wet laser welding was conducted on Ti-4Al-2V alloy using varying laser power. The microstructure and properties of the welding joints were characterized and analyzed. The microstructure of the heat-affected zone and fusion zone in the welding joints are not significantly different from those of welding in air, but a mixed oxide layer composed of Al2O3 and TiO2 is formed on the surface of the fusion zone. Due to internal stress, a large number of cracks initiate on the oxide layer and propagate to the joints. In the 4 kW and 5 kW joints, a penetrating crack formed due to the excessive accumulation of internal stress breaking up the α phase. The mechanical properties of the joints are significantly affected by the laser power. The tensile strength of the 3 kW and 4 kW joints is comparable to that of the base metal, which is about 600 MPa, while the 5 kW joint shows brittle fracture with no plastic deformation and 228 MPa strength. This research lays a solid foundation for understanding the underwater wet laser welding behavior of titanium alloys. [ABSTRACT FROM AUTHOR]

For the dry storage of Canada Deuterium Uranium (CANDU) spent nuclear fuels, the integrity of Zircaloy-4 fuel cladding has to be verified. However, the formation of ~10 µm-thick oxide layers in typical CANDU reactor operating conditions takes several years, which makes sample preparation a slow process. To overcome such limitations, in this study, an accelerated formation of an oxide layer on Zircaloy-4 cladding tube was developed with a combination of high-temperature water corrosion (HT-WC) and air oxidation (AO). First, Zircaloy-4 tubes were corroded in oxygenated (2 ppm dissolved oxygen) high-temperature water (360 °C/19.5 MPa) for 500 h. Then, the tubes were air-oxidized at 500 °C for 30 h. Finally, the tubes were corroded again in HT-WC for 500 h to produce ~10 µm-thick oxide layers. The morphology and characteristics of the oxide layer in each step were analyzed using X-ray diffraction, scanning and transmission electron microscopy. The results showed that the oxide layer formed in the accelerated method was comparable to that formed in HT-WC in terms of morphology and oxide phases. Thus, the accelerated oxide formation method can be used to prepare an oxidized Zircaloy-4 cladding tube for CANDU fuel integrity analysis. [ABSTRACT FROM AUTHOR]

The supercritical water-cooled reactors (SWCR) belong to Generation IV of reactors. These reactors have a number of advantages over currently operating WWERs and PWRs. These advantages include higher thermal efficiency, a more simplified unit design, and the possibility of incorporating it into a closed fuel cycle. It is therefore necessary to identify candidate materials for the SWCR and validate the safety and effectiveness of their use. 12Cr ferritic-martensitic (F/M) stainless steel is considered a candidate material for SWCR internals. Radiation embrittlement and corrosion cracking in the primary circuit coolant environment are the main mechanisms of F/M steels degradation during SWCR operation. Here, the stress corrosion cracking (SCC) in supercritical water at 390 and 550 °C of 12Cr F/M steel irradiated by neutrons to 12 dpa is investigated. Autoclave tests of specially designed disk specimens in supercritical water were performed. The tests were carried out under different constant load (CL), temperature 450 °C, and pressure in autoclave 25 MPa. The threshold stress, below which the SCC initiation of irradiated 12Cr F/M steel does not occur, was determined. [ABSTRACT FROM AUTHOR]

As a lightweight construction material, aluminum plays a key role in weight reduction and, thus, sustainability in the transport industry. The brazing of aluminum and its alloys is impeded by the natural passivating oxide layer, which interferes with the brazing process. The presented study investigates the possibility of using a thermal silane-doped argon plasma to reduce this oxide layer in situ and thus eliminating the need to use hazardous chemical fluxes to enable high-quality brazing. Using plasma spectroscopy and an oxygen partial pressure probe, it was shown that a silane-doped argon plasma could significantly reduce the oxygen concentration around the plasma in a thermal plasma brazing process. Oxygen concentrations below 10−16 vol.-% were achieved. Additionally, metallographic analyses showed that the thickness of an artificially produced Al2O3-Layer on top of AlMg1 samples could be substantially reduced by more than 50%. With the oxide layer removed and inhibition of re-oxidation, silane-doped plasma brazing has the potential to become an economically efficient new joining method. [ABSTRACT FROM AUTHOR]

The article presents the effect of anodizing parameters of the EN AW-5251 aluminum alloy on the thickness and roughness of Al2O3 layers as well as their wettability and tribological properties in a sliding combination with the T7W material. The input variables were the current density of 1, 2, 3 A/dm2 and the electrolyte temperature of 283, 293, 303 K. The tribological tests were performed on the T-17 tester in reciprocating motion, in conditions of technically dry friction. The tests were carried out on a 15 km road with a constant average slip speed of 0.2 m/s and a constant unit pressure of 1 MPa. The measurement of the wettability of the layers was performed using the sitting drop method, determining the contact angles on the basis of which the surface free energy was calculated. The profilographometric measurements were made. The analysis of the test results showed that the anodizing parameters significantly affect the thickness of the Al2O3 layers. The performed correlation analysis also showed a significant relationship between the roughness parameters and the wettability of the surface of the layers, which affects the ability to create and maintain a sliding film, which in turn translates into sliding resistance and wear of the T7W material. The analysis of friction and wear tests showed that the layer with hydrophobic properties produced at a current density of 1 A/dm2 in an electrolyte at a temperature of 283 K is the most favorable for sliding associations with T7W material. [ABSTRACT FROM AUTHOR]

The growing demand for implants has seen increasing interest in the introduction of new technologies and surface modification methods of metal biomaterials. This research aimed to produce and characterize a porous layer grown on austenitic stainless steel 316L, obtained via the anodization process near the micro-arc oxidation, i.e., low voltage micro-arc oxidation (LVMAO). The discussed layer significantly influences the properties of metallic biomedical materials. The surface topography, layer thickness, surface roughness, pore diameter, elemental composition, crystal structure, and surface wettability were assessed for all anodized layers, together with the resultant corrosion resistance. Attention was paid to the influence of the process parameters that affect the specification of the produced layer. The obtained results showed surface development and different sized pores in the modified layers, as well as an increase in corrosion resistance in the Ringer's solution. [ABSTRACT FROM AUTHOR]

Titanium Grade 4 (Ti G4) is the most commonly used material for dental implants due to its excellent mechanical properties, chemical stability and biocompatibility. A thin, self-passive oxide layer with protective properties to corrosion is formed on its surface. However, the spontaneous TiO2 layer is chemically unstable. In this work, the impact of autoclaving time on corrosion resistance of Ti G4 in artificial saliva solution with pH = 7.4 at 37 °C was studied. Ti G4 was sandblasted with white Al2O3 particles and autoclaved for 30–120 min. SEM, EDS, 2D roughness profiles, confocal laser scanning microscopy, and a Kelvin scanning probe were used for the surface characterization of the Ti G4 under study. In vitro corrosion resistance tests were conducted using open circuit potential, polarization curves, and electrochemical impedance spectroscopy measurements. It was found that Sa parameter, electron work function, and thickness of the oxide layers, determined based on impedance measurements, increased after autoclaving. The capacitive behavior and high corrosion resistance of tested materials were revealed. The improvement in the corrosion resistance after autoclaving was due to the presence of oxide layers with high chemical stability. The optimal Ti G4 surface for dentistry can be obtained by sandblasting with Al2O3 with an average grain size of 53 µm, followed by autoclaving for 90 min. [ABSTRACT FROM AUTHOR]

The oxide layer on the surface of Sn-0.4Ti alloy and its removal mechanism were investigated by coalitional analyses, using XPS and TEM technologies. The results show that a compact SnO1.65 oxide layer of less than 4 nm in thickness exists on the surface of Sn-0.4Ti alloy. A large number of TiO2 nanoparticles with scale of several to tens of nanometers were grown in Sn-0.4Ti matrix by depleting SnO1.65 while welding at 800 °C. These nanoparticles were adhered to the interfacial layer between Sn-0.4Ti alloy and quartz glass, which was formed by the reaction of Sn-0.4Ti and SiO2 after SnO1.65 removal from the Sn-0.4Ti. This work may promote further works on Sn-Ti design to further improve the welding quality between Sn-Ti alloy and quartz glass, and also provide a feasible research idea to remove the oxide layer on the surfaces of solders. [ABSTRACT FROM AUTHOR]