Research on Evaluation Technology of Low Temperature Cold Start Performance of Hydraulic Oil

In order to comprehensively test the low temperature cold start performance of hydraulic oil and ensure their use effectiveness to the fullest, the idea of low temperature cold start performance index is proposed, so as to comprehensively evaluate the low temperature capability. Firstly, the cold start performance index system of hydraulic oil tested in low temperature environment is constructed, so as to describe its low temperature capability from multiple angles and in a comprehensive manner; secondly, for different index types, the corresponding data collection methods and data analysis methods are clarified, and the low temperature cold start performance of hydraulic fluid is evaluated. Finally, using the method as an example for three oils, the index types and assessment results are given to further illustrate the scientific nature of the research method. The research content can provide some technical support for the evaluation of the low temperature cold starting performance test of hydraulic winches.

Contribution in Optimization of Honeycomb Abradable Seals Structure

The abradable coatings had significantly enhanced turbomachinery performance by acting as a sacrificial seal between rotating blades and stationary casing. Further improvement in seal design to meet the higher energy demand and increase the service time has been the key challenges to solve in the gas turbine industry. Honeycomb seals have become the industry standard clearance seal technique due to their unique design and high structural strength with minimum weight. The present study proposes a concept to form a thermal shock resistance structure to achieve higher temperature capability and improve the reliability of abradable seal structures. A cavity layer of honeycomb seal structure made of SS 321 alloy was coated with advanced high-temperature ZrO2+7.5%Y2O3+4% polyester seal material using TriplexPro-210 plasma spray system. The integrity of a seal structure was assessed by a cross-sectional analysis and evaluation of the coating microstructure. Additionally; the microhardness test was performed to estimate coating fracture toughness; and Object-Oriented Finite Element analysis was used to assess its thermo-mechanical performance. The concept proposed in this study should be further validated to develop the most capable innovative technology for advanced gas turbine abradable seal structures.

Effect of Supercritical CO2 on Steel Ductility at 450°-650°C

The compatibility of ferritic-martensitic (FM) and conventional and advanced austenitic steels with supercritical CO2 (sCO2) is being explored at 450°–650°C to determine their maximum temperature capability. In addition to measuring reaction kinetics and reaction product thickness, bulk carbon content and post-exposure room temperature tensile properties were assessed by exposing both alloy coupons and 25 mm long dogbone tensile specimens. After 1–2 kh exposures in 300 bar research grade (RG) sCO2, ∼9 and 12%Cr FM steels had similar behavior under these conditions. Consistent with the literature, higher Cr and Ni contents in alloy 316H provided lower reaction rates at 450° and 550°C, but limited benefit at 650°C with similar degradation of tensile properties and C ingress observed. An advanced austenitic Nb-modified 20Cr-25Ni alloy 709 provided the best compatibility even at 650°C with no C uptake detected after 1 kh and no significant loss in room temperature tensile properties after exposure. A clear correlation was observed under these conditions between the formation of a thin, protective Cr-rich oxide scale and the prevention of C ingress and tensile property degradation at 650°C.

Probing Phase Transitions and Magnetism in Minerals with Neutrons

The development of sophisticated sample environments to control temperature, pressure, and magnetic field has grown in parallel with neutron source and instrumentation development. High-pressure apparatus, with high- and low-temperature capability, novel designs for diamond cells, and large volume presses are matched with next-generation neutron sources and moderator designs to provide unprecedented neutron beam brightness. Recent developments in sample environments are expanding the pressure–temperature space accessible to neutron scattering experiments. Researchers are using new capabilities and an increased understanding of the fundamentals of structural and magnetic transitions to explore new territories, including hydrogenous minerals (e.g., ices and hydrates) and magnetic structural phase diagrams.

SPIN modification for low-temperature experiments

The SPectrometer for Ice Nuclei (SPIN) has been modified to access ice nucleation at low temperatures. The modification consists of a reconfiguration of components from SPIN's cooling system to provide refrigerant with a low boiling point to the chamber. We describe the setup modification and determine the temperature and humidity range accessible to experiments. The modification extends the measurement range of SPIN to 208 K, which enables measurements in the temperature regime relevant for ice formation in cirrus clouds. This addition of low-temperature capability allows for far more comprehensive measurements of the temperature- and humidity-dependent ice nucleation of test substances, to investigate fundamentals of ice nucleation mechanisms. We present exemplary data of heterogeneous ice nucleation on silver iodide and homogeneous ice nucleation in solution droplets to demonstrate the usefulness of the modified SPIN setup for precision measurements to detect discrepancies between experiments and widely used theories.

Na2SO4 + V2O5 Corrosion Behavior of BaNd2Ti3O10 for Thermal Barrier Coating Applications

BaNd2Ti3O10 has been considered as a promising thermal barrier coating (TBC) candidate material, which reveals many advantages over the widely used TBC material of yttria partially stabilized zirconia, such as lower thermal conductivity, better high-temperature capability, and higher resistance to environmental deposits corrosion. In this study, the hot corrosion behavior of BaNd2Ti3O10 in Na2SO4 + V2O5 molten salt at 900 °C and 1000 °C is investigated. Exposed to the salt for 4 h at 900 °C, BaNd2Ti3O10 pellets had an obvious reaction with the salt, forming corrosion products of NdVO4, TiO2, and BaSO4, and the reaction layer was ~30 μm, beneath which no salt trace could be found. Prolonging the corrosion time to 20 h, the type of the corrosion products had no change. At an elevated corrosion temperature of 1000 °C for 4 h, the corrosion products were still NdVO4, TiO2, and BaSO4, but NdVO4 revealed a significant growth, which fully covered the pellet surface. The mechanisms by which the corrosion reaction between BaNd2Ti3O10 and the molten salt occurred were discussed.

SPIN modification for low temperature experiments

The SPectrometer for Ice Nuclei (SPIN) has been modified to access ice nucleation at low temperatures. The modification consists of a reconfiguration of components from SPIN's cooling system to provide refrigerant with a low boiling point to the chamber. We describe the setup modification and determine the temperature and humidity range accessible to experiments. The modification extends the measurement range of SPIN by more than 20 K to the temperature regime relevant for ice formation in cirrus clouds. This addition of low temperature capability allows for far more comprehensive measurements of the temperature- and humidity- dependent ice nucleation of test substances, to investigate fundamentals of ice nucleation mechanisms. We present exemplary data of heterogeneous ice nucleation on silver iodide and homogeneous ice nucleation in solution droplets to demonstrate the usefulness of the modified SPIN setup for precision measurements to detect discrepancies between experiments and widely used theories.

Extreme Environment Integrated Circuits Based on Enhancement Mode SiC JFETs

This paper presents results on developing high temperature capable SiC JFET based IC technology that can operate at temperatures up to 500 °C. All JFET devices are fully planar, formed by ion implantation, and the device design allows the use of semi-insulating or conductive SiC substrates. Basic analog and logic ICs were built in order to demonstrate the technology high temperature capability. All circuits used enhancement mode n-channel JFETs as active transistors, and depletion mode transistors as active loads. The logic circuits built included NOT, NAND, and NOR gates. The analog circuits built included a simple one-stage operational amplifier. JFETs and ICs were packaged in ceramic packages and tested at temperatures up to 500 °C.

On the Development Concept for a New 718-Type Superalloy with Improved Temperature Capability

The superalloy 718 stands out for its excellent manufacturability and strength at ambient temperature. However, its application temperature is limited to about 650 °C due to the instability of the γ’’ precipitates. Here, we provide an in-depth account of an alloy development concept, allowing for the design of superalloys with 718-type properties, yet with a significantly improved microstructural stability. The article begins with a detailed discussion on how the microstructural and chemical composition must be altered to achieve this objective. Then, model alloys were used to explore and validate the outlined strategy. Finally, it is shown how these considerations ultimately led to a new 718-type superalloy with far more improved microstructural stability— namely, VDM Alloy 780. The introduction of a large amount of Co as a substitute for Fe (and partially Ni) is the most important element of our alloy development concept in terms of chemical composition. The most important microstructural feature is the introduction of low solvus temperature, high misfit γ´-strengthening, replacing γ´´-hardening.