Study on creep behavior and microstructure of a Fe–Cr–Al–Nb–W ferrtic heat-resistant steel based on C, N and Al element control

In this work, the effects of C, N, and Al on the microstructures and creep properties of Fe–Cr–Al–Nb–W ferritic alloys were investigated through scanning electron microscopy, x-ray diffractometry, as well as uniaxial creep testing and hardness testing. The results demonstrated that the matrix of the Fe–Cr–Al–Nb–W heat-resistant steel was ferrite, while the precipitation phases were Laves phases, M _23 C _6 carbides and MX nitride phases. M _23 C _6 and MX precipitated at grain interior, Laves phases precipitated at grain interior, grain boundary and around MX phases. C, N and Al affected microstructure and creep of heat-resistant steel. As the Al content increased or as N content decreased along with the C increase, the average diameter of the Laves phases, along with M _23 C _6 and MX phase grain interior decrease. Moreover, the unit density increased and the phase spacing decreased, which led to the minimum creep rate decrease and creep rupture time increase. Compared to M _23 C _6 , Laves and MX phases mainly affected the alloy creep strength. The decrease of Laves phase continuity coefficient (ratio of Laves phase particle spacing and size) on the grain boundary was conducive to the plasticity improvement of heat-resistant steel

The inhibitive effect of artificial seawater on magnesium corrosion

The corrosion behavior of pure magnesium (Mg) immersed in 3.5 wt% NaCl and artificial seawater is evaluated by immersion test, electrochemical impedance spectroscopy (EIS), polarization curve, scanning electrochemical microscopy (SECM), and corrosion morphology analysis. The results show that the corrosion rate of the pure Mg in the artificial seawater is nearly a half of that in the 3.5 wt% NaCl, and the serious localized corrosion of Mg in the NaCl is inhibited in the artificial seawater. The main constituents MgCl and NaSO in artificial seawater are found to be inhibitive for the corrosion of Mg. The presence of Mg ions could facilitate the formation of Mg(OH) film and thus to some extent retard the dissolution of Mg. The SO ions in the artificial seawater might be absorbed competitively against Cl on the Mg surface to retard the corrosion of Mg. The corrosive and inhibitive effects of other anions and cations on Mg dissolution in the artificial seawater were also briefly analyzed

Application of Additives in Platycladus orientalis (L.) Franco Tending Shreds Compost in Forest

This study aimed to explore the effects of different additives on tending shreds of Platycladus orientalis (L.) Franco. Two different additives (priming 0.2% and common compost 0.2%) combined with C, N, and P adjustment of raw material treatments were tested on the temperature, moisture, EC, pH, lignocellulose degradation rate, nutrient content, and toxicity of compost. Priming made the compost temperature rise rapidly, and the peak temperature of the composting group with priming reached 51 °C. At the end of composting, the moisture in each treatment from high to low was in the order: common compost > priming > C/N, C/P adjustment only > control group. The increase of EC in the treatments with additives was great, and the peak value of EC in the treatment of priming was 1.30 ms·cm−1, which was 3.9 times higher than that of the control group. At the end of composting, the decomposition rate of cellulose in priming compost was 1.7 times higher than that in the control group, and the hemicellulose decomposition rate in the common compost group was 3.2 times higher than that in the control group. By the end of composting, the pH value of the composts in additive treatments was above 7.0, and the pH value of the priming treatment was the highest (7.5). The highest content of organic matter was found in the priming treatment, which was 52%, 1.7 times higher than that in the control group. The total nutrient content (TN + K2O + P2O5) of additive treatments was higher than 5.0%, and the priming treatment was 2.7% higher than that of the control group. By the end of composting, the germination rate and germination index ranged from 88% to 91% and 60% to 81%. Except for the control group, the C/N ratio of other treatments decreased to below 25. Additives can accelerate the decomposition of raw materials, shorten the composting cycle, and improve the quality of composts, and the effect of adding priming is the most significant

ASP Flooding: Theory and Practice Progress in China

In low oil price era, it seems that ASP flooding has little market. However, ASP progress in China shows that ASP flooding is good technology to help oil companies thrive and make profit. Since 2014, ASP flooding has entered industrial application in Daqing oilfield. ASP flooding production in 2015 is 3.5 million ton, 9% of the oilfield’s total production of Daqing oilfield. There are 22 ASP flooding blocks in Daqing, containing 7231 wells and 3 are new blocks in 2016. Obviously, more and more ASP flooding is being carried out. Another large ASP flooding field test in high temperature (80°C) in Henan oilfield has got staged incremental oil recovery of 7.7%. Latest theory and application in ASP flooding in China are reviewed to help ASP flooding go from success to more application. Weak alkali is better than strong alkali ASP flooding. Relation between viscosity and IFT is discussed. This paper also explains why weak alkali ASP flooding is promoted in Daqing after 12 field tests on strong alkali one. ASP flooding can be a great help to survive low oil price

Influence of thermal ageing on creep rupture mechanism and creep life of P92 ferritic steel

In order to analyze the effect of thermal ageing on creep rupture mechanism and establish a method for predicting the creep rupture life of P92 heat-resistant steel under thermal ageing, creep tests were performed on P92 steel specimens, aged at 650 °C for different times under different applied stresses. Optical microscopy and scanning electron microscopy were utilized to observe the microstructure after thermal ageing and creep rupture. Voids and cracks were distributed in the grains of P92 steel before thermal ageing, whereas the voids were clearly distributed around M _23 C _6 precipitates and Laves phase along sub-grain boundaries after thermal ageing. The creep damage tolerance factor of the unaged and short-time aged samples ranged from 2.5 to 5, and the creep rupture was caused by dislocation movement. After high-temperature thermal ageing for 3000 h, the damage tolerance factor increased to > 5 and creep rupture was caused by precipitate coarsening. A theoretical method was established to predict the creep rupture life of heat-resistant P92 steel under thermal ageing, providing consistent results with the American Society of Mechanical Engineers (ASME) long-term test and trend

Proper Use of Capillary Number in Chemical Flooding

Capillary number theory is very important for chemical flooding enhanced oil recovery. The difference between microscopic capillary number and the microscopic one is easy to confuse. After decades of development, great progress has been made in capillary number theory and it has important but sometimes incorrect application in EOR. The capillary number theory was based on capillary tube bundles and Darcy’s law hypothesis, and this should always be kept in mind when used in chemical flooding EOR. The flow in low permeability porous media often shows obvious non-Darcy effects, which is beyond Darcy’s law. Experiments data from ASP flooding and SP flooding showed that remaining oil saturation was not always decreasing as capillary number kept on increasing. Relative permeability was proved function of capillary number; its rate dependence was affected by capillary end effects. The mobility control should be given priority rather than lowering IFT. The displacement efficiency was not increased as displacement velocity increased as expected in heavy oil chemical flooding. Largest capillary number does not always make highest recovery in chemical flooding in heterogeneous reservoir. Misuse of CDC in EOR included the ignorance of mobility ratio, Darcy linear flow hypothesis, difference between microscopic capillary number and the microscopic one, and heterogeneity caused flow regime alteration. Displacement of continuous oil or remobilization of discontinuous oil was quite different

Numerical analysis on heat transfer process in the coke oven with the multi-chamber coupling mathematical model

The influence of the thermal conductivity of silica bricks on the coking process as an important component of the coking and combustion chambers is still unclear. A multi-chamber coupling mathematical model of a coke oven is developed to investigate the energy-saving effect of using high thermal conductivity silica bricks in the coke oven. The model is validated using measured temperatures of coal and flue gas bed in a coke oven in operation for a coking cycle. Temperature variation and its distribution in the coking chamber, combustion chamber, and heating wall are simulated for the coke oven using silica bricks with different thermal conductivities. The obtained results showed that compared with the use of common silica bricks, coking time of one cycle can be reduced by ∼60 min, with a decreased consumption of fuel gas by ∼4.9%. The enhancement of heat transfer from the flue gas to the heating wall and the heating wall to coal using silicon bricks with high thermal conductivity can effectively shorten not only the temperature difference between the two sides of the heating wall but also reduce the mean flue temperature of the flue gas by ∼24.5 °C

Nonlinear Mid‐Infrared Metasurface based on a Phase‐Change Material

The mid-wave infrared (MWIR) spectral region (3-5 {\mu}m) is important to a vast variety of applications in imaging, sensing, spectroscopy, surgery, and optical communications. Efficient third-harmonic generation (THG), converting light from the MWIR range into the near-infrared, a region with mature optical detection and manipulation technologies, offers the opportunity to mitigate a commonly recognized limitation of current MWIR systems. In this work, we present the possibility of boosting THG in the MWIR through a metasurface design. Specifically, we demonstrate a 30-fold enhancement in a highly nonlinear phase change material Ge2Sb2Se4Te1 (GSST), by patterning arrays of subwavelength cylinders supporting a magnetic dipolar resonance. The unprecedented broadband transparency, large refractive index, and remarkably high nonlinear response, together with unique phase-change properties, make GSST-based metasurfaces an appealing solution for reconfigurable and ultra-compact nonlinear devices operating in the MWIR.Comment: 15 pages, 3 figure