Effect of Cryogenic Treatment on Microstructure, Mechanical Properties and Distortion of Carburized Gear Steels

The effects of cryogenic treatment and low temperature tempering on the microstructure, mechanical properties and distortion of the 20Cr2Ni4A and 17Cr2Ni2MoVNb carburized gear steels were investigated. The results showed that the case hardness of the experimental steels was increased after the cryogenic treatment, due to the decrease of the retained austenite content and the precipitation of the tiny carbides. The wear resistance of the two steels after cryogenic treatment was improved, although the wear mechanisms were different for 17Cr2Ni2MoVNb and 20Cr2Ni4A steels. The distortion of the Navy C-ring specimens underwent shrinkage before expansion during the cryogenic process, and the distortion of 17Cr2Ni2MoVNb steel was smaller than that of 20Cr2Ni4A steel.

Development of Fe-11Al-xMN alloy steel on cryogenic temperatures

This research is focused on increasing the reliability of Fe-11Al-Mn by combining the properties of Mn and the superiority of Fe-Al-C under cryogenic temperature. Three Fe-11Al-Mn alloys with compositions of 15 wt % Mn (F15), 20 wt % Mn (F20), and 25 wt % Mn (F25) were investigated. The cryogenic process uses liquid nitrogen in a temperature range of 0–196 °C. Hardness testing using the Vickers method and SEM was used to analyze the microstructure. X-ray diffraction (XRD) testing was conducted to ensure the Fe-11Al-Mn alloy phase and corrosion testing was carried out using the three-electrode cell polarization method. With the addition of Mn, the Vickers hardness of the Fe-11Al-Mn alloy decreased from 331.50 VHN at 15 wt % to 297.91 VHN at 25 wt %. The value of tensile strength and fracture elongation values were 742.21 MPa, 35.3 % EI; 789.03 MPa, 41.2 % EI; and 894.42 MPa, 50.2 % EI, for F15, F20, and F25, respectively. An important factor for improving the performance of cryogenic materials is the impact mechanism. The resulting impact toughness increased by 2.85 J/mm2 to 3.30 J/mm2 for F.15 and F25, respectively. The addition of the element Mn increases the corrosion resistance of the Fe-11Al-Mn alloy. The lowest corrosion rate occurs at 25 % wt Mn to 0.016 mm/year. Based on the results, the F25 alloy has the highest mechanical and corrosion resistance of the three types of alloys equivalent to SS 304 stainless steel. The microstructure of Fe-11Al-Mn alloy was similar between before and after cryogenic temperature treatment, this condition showed that the microstructure did not change during the process. From the overall results, the Fa-11Al-Mn alloy is a promising candidate for material applications working at cryogenic temperatures by optimizing the Mn content

Tackling Dissipative Components Based on the SPECO Approach: A Cryogenic Heat Exchanger Used in Natural Gas Liquefaction

The cryogenic industry has been experiencing continuous progress in recent years, primarily due to the global development of oil and gas activities. Natural gas liquefaction is a cryogenic process, with the refrigeration system being crucial to the overall process. The objective of the study presented herein is to carry out an exergoeconomic assessment for a dual nitrogen expander process used to liquefy natural gas, employing the SPecific Exergy COsting (SPECO) methodology. The air coolers and throttling valve are dissipative components, which present fictitious unit cost rates that are reallocated to the final product (Liquefied Natural Gas). The liquefaction process has an exergy efficiency of 41.89%, and the specific cost of liquefied natural gas is 292.30 US$/GJ. It was verified that this cost increased along with electricity. The highest exergy destruction rates were obtained for Expander 1 and Air cooler 2. The highest average cost per exergy unit of fuel was obtained for the vertical separator, followed by Air coolers 1 and 2. An assessment of the exergoeconomic factor indicated that both expanders could benefit from a decrease in exergy destruction, improving the exergoeconomic performance of the overall system. Regarding the relative cost difference, all compressors presented high values and can be enhanced with low efforts.

Liquid sulfur dioxide production method based on sulfur and oxygen. R&D of economically feasible method

The article shows the relevance of the industrial production of liquid sulfur dioxide, as well as the fields of its application. Herewith there is provided a brief description of the known methods for the production of liquid sulfur dioxide: the use of roast gas; sulfur-oleum method; multi-stage condensation; low temperature cryogenic process; oxidation of sulfur with oxygen under its stoichiometric deficiency. In the course of the analysis, the main shortcomings of the considered methods were identified, which made it possible to develop an innovative version of the process scheme. Based on the data obtained, JSC “NIUIF” has developed and patented a method for producing liquid sulfur dioxide, the main raw material of which is sulfur and oxygen under its stoichiometric deficiency. The principal difference of the proposed industrial scheme is the use of technical oxygen instead of air blast and the use of a sulfur furnace and a sulfur vapor condenser combined in one housing in the apparatus scheme. The proposed solution significantly reduces energy consumption and eliminates the possibility of liquid sulfur crystallizing inside the equipment. Therefore, this scheme can be considered more reliable and reasonable in comparison with the existing ones. Also, in the process scheme of the developed unit, the production of 1 ton of liquid sulfur dioxide consumes significantly less energy than in the existing technologies. To determine the design parameters of the equipment and master the processes, the article describes a lab unit for producing liquid sulfur dioxide, developed and already installed at JSC "NIUIF". At the moment, experiments are carried out at the facility for the purpose of adjusting the operation mode and collecting the physical and chemical process data.

Comparison between Bosch and STiGer Processes for Deep Silicon Etching

The cryogenic process is well known to etch high aspect ratio features in silicon with smooth sidewalls. A time-multiplexed cryogenic process, called STiGer, was developed in 2006 and patented. Like the Bosch process, it consists in repeating cycles composed of an isotropic etching step followed by a passivation step. If the etching step is similar for both processes, the passivation step is a SiF4/O2 plasma that efficiently deposits a SiOxFy layer on the sidewalls only if the substrate is cooled at cryogenic temperature. In this paper, it is shown that the STiGer process can achieve profiles and performances equivalent to the Bosch process. However, since sidewall passivation is achieved with polymer free plasma chemistry, less frequent chamber cleaning is necessary, which contributes to increase the throughput.

Effects of Aging and Deep Cryogenic Treatment on Wear Behavior of Al7075 Alloy

This study investigated the effects of aging and deep cryogenic treatment applied to Al7075 alloy on hardness and wear behavior. In this context, two different categories were created for the aging process. For the first group, after solutionizing the samples at 520 °C for 2 h, aging was applied at 120 °C for 12 h to reach 177 HV hardness. In the second group, after solutionizing at 520 °C for 2 h, the aging process was applied at 200 °C for 8 h to reach a hardness value of 164 HV. In addition, deep cryogenic treatment (12 h, 24 h, and 36 h at −140 °C) was applied to the samples after the solutionizing and aging processes. The pin-on-disc wear test was carried out according to the ASTM G99 standard in order to examine the effects of the aging and cryogenic processes on wear behavior. The highest wear resistance was obtained with the Al7075 sample aged at 120 °C for 12 h followed by the 12-h deep cryogenic treatment. Hardness values and wear test results showed that the applied cryogenic process had positively affected the wear behavior.

Mapping the Main Characteristics of Permafrost on the Basis of a Permafrost-Landscape Map of Yakutia Using GIS

The purpose of this article was to compile four separate digital thematic maps of temperature and ice content of permafrost, the active layer thickness, and cryogenic processes in Yakutia as a basis for assessing changes to modern climate changes and anthropogenic disturbances. In this work, materials on permafrost were used, serving as the basis for compiling a permafrost landscape map of the Republic of Sakha (Yakutia). The maps were compiled using ArcGIS software, which supports attribute table mapping. The ground temperature and active layer thickness maps reflected landscape zonality and regional differences. Peculiarities of genetic types of Quaternary deposits and climatic conditions reflected the ice content of surface sediments and cryogenic process distribution maps. One of the most common is ground temperatures from −2.1 to −4.0 °C, which were found to occupy about 37.4% of the territory of Yakutia. More than half of the region was found to be occupied by permafrost landscapes with a limited thickness of the active layer up to 1.1 m. Ice-rich permafrost (more than 0.4 in ice content) was found to be typical for about 40% of the territory. Thermokarst is the most hazardous process that occurs in half of Yakutia.