Coatings of nanocrystalline metallic wires on steel substrate: mechanical characteristics of coating layer

Coatings are produced by wire arc spraying on a steel surface and the effect of coating thickness on the coating characteristics in terms of microhardness, residual stress and friction coefficient are examined. The wire used during coating is composed of FeCrBMnSi, which comprises nanocrystalline and amorphous phases. The twin wire arc spray system was incorporated to generate different coating thicknesses on steel substrate. The analytical tools including three-dimensional imaging optical and scanning electron microscopes, energy dispersive spectroscopy and X-ray diffraction (XRD) are used to assess the coating characteristics. It is found that the surface texture and surface roughness of the coatings change with coating thickness. Thus, reducing the coating thickness results in slightly increased texture height and surface roughness. Microhardness is almost 15% higher for the thin coating (300?μm) than the thick coating (550?μm). The residual stress developed in the coatings is tensile and it changes with coating thickness, such that it reduces for thick coating.     

Influence of La2O3 addition on nano indentation hardness and residual stress of Stellite 6 coating prepared by plasma cladding

One of the problems limiting the application of Stellite 6 coating is the residual stress resulting in cracks in the coating easily. In order to reduce the residual stress and increase the nano-indentation hardness, La₂O₃ was added to Stellite 6 coating in this study, and the influence on the microstructure, nano indentation hardness and residual stress of the coatings were investigated by scanning electron microscopy (SEM) with energy dispersive spectrum (EDS), X-ray diffraction (XRD) and nano-indentation tester. Results indicate that the addition of La₂O₃ leads to the phenomenon that the dendrite is partly transformed into the equiaxed grain, which results in the grain refinement. The nano-indentation hardness of coatings is improved, which is attributed to the fine-grain strengthening and dispersion strengthening effect of La₂O₃. With the addition of La₂O₃, the residual stress in coatings is decreased significantly. Especially, when the content of La₂O₃ is 0.8 wt%, the nano indentation hardness increases by 1.31 times and residual stress decreases to 20 percent, compared with coating without La₂O₃.     

湿法喷丸处理YG8合金表面残余应力分析及对性能的影响

采用湿法喷丸工艺对YG8硬质合金进行表面处理,旨在提高材料的性能.通过X射线衍射法对不同喷射条件处理的合金表面残余应力及其深度分布进行了分析,并研究了残余应力对力学性能的影响.研究表明,湿法喷丸处理在硬质合金表层内产生残余压应力,喷射压力和喷射时间对残余应力及分布有显著影响,该应力及分布有利于材料性能的提高.应用该处理方法,在喷射压力为0.5MPa、喷射时间为2min的条件下,硬质合金的抗弯强度提高约11%,洛氏硬度为89.64HRA,磨损量减少36%.     

A diathesis-stress model of posttraumatic stress disorder: Ecological, biological, and residual stress pathways.

The symptoms captured within the contemporary diagnostic definition of posttraumatic stress disorder (PTSD) have been studied for more than 100 years. Yet, even with increasingly advanced discoveries regarding the etiology of PTSD, a comprehensive and up-to-date etiological model that incorporates both medical and psychological research has not been described and systematically studied. The diathesis-stress model proposed here consolidates existing medical and psychological research data on etiological factors associated with PTSD into 3 causal pathways: residual stress, ecological, and biological. In combination, these pathways illuminate how PTSD might develop and who might be at higher risk for developing the disorder. Research and treatment implications related to the diathesis-stress model are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of welding processes on tensile, impact, hardness and microstructure of AISI 409M ferritic stainless joints fabricated using duplex stainless steel filler metal

 The present investigation is aimed at to study the effect of welding processes such as shielded metal arc welding, gas metal arc welding and gas tungsten arc welding on tensile and impact properties of the ferritic stainless steel conforming to AISI 409M grade. Rolled plates of 4 mm thickness were used as the base material for preparing single pass butt welded joints. Tensile and impact properties, micro hardness, microstructure and fracture surface morphology of the welded joints have been evaluated and the results are compared. From this investigation, it is found that gas tungsten arc welded joints of ferritic stainless steel showed superior tensile and impact properties compared with shielded metal arc and gas metal arc welded joints and this is mainly due to the presence of finer grains in fusion zone and heat affected zone.     

低应力对U75V重轨钢等温转变过程组织及硬度的影响

相变过程是伴随应力而发生的,此应力往往不超过对应温度下的屈服强度。分析了U75V重轨钢在等温转变过程中,低应力对相变过程的组织形貌和硬度的影响,通过Gleeble 3500热模拟机施加0,-20,-30,-40 MPa不同的低应力后发现:随着应力的增大,珠光体的片间距明显减小,同时片状珠光体质量分数也减少,粒状珠光体质量分数增多;硬度先呈现出升高的趋势,随着应力值增大到-30 MPa后,硬度开始急剧下降。     

Q235钢表面氩弧熔覆MoNiSi/Ni_3Si金属硅化物复合涂层组织与性能研究

以Mo粉、Si粉、Ni粉为原料,采用氩弧熔覆技术在Q235钢基材表面原位合成了MoNiSi/Ni3Si金属硅化物复合涂层,分析和测试了涂层的显微组织、显微硬度和耐磨性.结果表明:在Q235钢表面成功制备了以MoNiSi/Ni3Si为基体,以金属硅化物MoNiSi为增强相的复合涂层.性能分析结果表明:涂层的显微硬度可达1 000HV,涂层耐磨性较基体提高12倍.     

Electric arc furnace dust-coal composite pellet: effects of pellet size,dust composition,and additives on swelling and zinc removal

Abstract

Electric arc furnace (EAF) dust-coal composite pellets were heated from room temperature to 1423 and 1468 K under flowing argon by means of two heating patterns (non-isothermal tests). Apparent volume variation, compressive strength after heating, and zinc removal efficiency were evaluated, the last as a function of the additives used in the present work. A decrease of pellet size (from 14 to 7 mm in diameter) as well as the presence of Portland cement contributed towards avoiding abnormal swelling caused by growth of iron whiskers, and, as a consequence, there was no significant decrease of compressive strength at ~1323 K. At 1397 K, highest zinc removal was obtained for pellets with 12 wt-%KCl, and reasons for this result are proposed.     

平面光栅电弧发射光谱法测定地球化学样品中银硼锡的影响因素探讨

Ag、B、Sn 3种元素在地球化学样品调查分析中占有独特的地位,然而B元素难挥发,Ag、Sn易挥发的特点决定了只能采用发射光谱法测定。在测定过程中,蒸发行为、钨片和排风风量等前处理方面因素对于其准确测定具有重要作用。以焦硫酸钾(K₂S₂O₇)、氟化钠(NaF)、三氧化二铝(Al₂O₃)、二氧化锗(GeO₂)和炭粉(C)为缓冲剂,锗(Ge)为内标,采用交流电弧发射光谱法,使用CCD-1平面光栅电弧发射光谱仪对影响地球化学样品中Ag、B、Sn的因素进行探讨。结果表明,易挥发元素Ag、Sn在14 s时谱线强度达到最大值,难挥发元素B在16 s时谱线强度达到最大值,摄谱最佳时间为30 s,钨片经过打磨和间隙的调整后,计算GBW07375、GBW07401和GBW07312等国家一级标准物质测定值的平均值与认定值的对数偏差(ΔlgC)和相对标准偏差(RSD,n=6)分别为0~0.02和2.30%~5.34%,满足正确度和精密度的要求。排风开至3/4风量时,计算GBW07375、GBW07401和GBW07312等国家一级标准物质测定值的平均值与认定值的对数偏差(ΔlgC)和相对标准偏差(RSD,n=6)分别为0~0.02和1.04%~8.32%。实验方法的正确度和精密度均满足要求,可用于地球化学样品中Ag、B和Sn的测定。     

平面光栅电弧发射光谱法测定地球化学样品中银硼锡的影响因素探讨

Ag、B、Sn 3种元素在地球化学样品调查分析中占有独特的地位,然而B元素难挥发,Ag、Sn易挥发的特点决定了只能采用发射光谱法测定。在测定过程中,蒸发行为、钨片和排风风量等前处理方面因素对于其准确测定具有重要作用。以焦硫酸钾(K₂S₂O₇)、氟化钠(NaF)、三氧化二铝(Al₂O₃)、二氧化锗(GeO₂)和炭粉(C)为缓冲剂,锗(Ge)为内标,采用交流电弧发射光谱法,使用CCD-1平面光栅电弧发射光谱仪对影响地球化学样品中Ag、B、Sn的因素进行探讨。结果表明,易挥发元素Ag、Sn在14 s时谱线强度达到最大值,难挥发元素B在16 s时谱线强度达到最大值,摄谱最佳时间为30 s,钨片经过打磨和间隙的调整后,计算GBW07375、GBW07401和GBW07312等国家一级标准物质测定值的平均值与认定值的对数偏差(ΔlgC)和相对标准偏差(RSD,n=6)分别为0~0.02和2.30%~5.34%,满足正确度和精密度的要求。排风开至3/4风量时,计算GBW07375、GBW07401和GBW07312等国家一级标准物质测定值的平均值与认定值的对数偏差(ΔlgC)和相对标准偏差(RSD,n=6)分别为0~0.02和1.04%~8.32%。实验方法的正确度和精密度均满足要求,可用于地球化学样品中Ag、B和Sn的测定。     

高频燃烧红外吸收法测定铜及铜合金管材内表面残碳量

铜及铜合金管材内表面残碳量的高低对产品的性能和使用寿命有重要影响.试样表面经新配制的硝酸(1+1)酸洗处理,以硝酸、磷酸、冰醋酸组成的混合酸进行抛光处理,以硫酸、铬酐、氯化钠加纯水配制的钝化液进行钝化处理,再用三氯乙烯超声清洗,经切割加工后,在1 100 W功率下采用红外吸收法进行测定,建立了铜及铜合金管材内表面残碳量...     

Selective laser melting of P20 mould steel: investigation on the resultant microstructure,high-temperature hardness and corrosion resistance

Additive manufacturing (AM) &; 3D printing can realise rapid delivery of high-quality and complex-geometry industrial product like steel mould with conformal cooling channels. In this paper, selective laser melting (SLM), a typical AM technique, was used to investigate the processing of P20 tool steel which is commonly used for plastic mould. SLM processing parameters, including scanning speed and laser power, were investigated to produce test specimens with high density. High cooling rate induced formation of refined dendrite and major crystalline phases in the as-printed P20 are identified largely as martensite, with an additional small portion of retained austenite. A subsequent tempering heat treatment has been done to eliminate these metastable phases and guarantee overall structural stability and mechanical property of the as-printed P20. Hardness at 250°C and corrosion resistance in 3.5?wt-% NaCl aqueous solutions were measured to evaluate the reliability of P20 mould steel under service, which show rather satisfactory results.     

碳含量对GH4199合金拉伸、持久性能及组织的影响

研究了碳含量对镍基变形高温合金GH4199拉伸、持久性能及显微组织的影响,并对碳含量变化所引起的组织及性能改变的原因进行了分析.结果表明:增加碳含量会阻止晶粒度长大,并明显改变碳化物的数量、形状及分布,碳化物类型主要以(W, Mo)6C为主,800℃长期时效500h后有M23C6析出,较低的碳含量对合金的拉伸及持久性能是有利的.     

酒钢CSP薄板坯中碳J55钢表面纵裂形成原因及控制

通过实验分析等方法,对酒钢J55钢薄板坯表面纵裂的形成机理进行了分析。结果表明,J55表面纵裂起因于结晶器弯月面初生坯壳厚度的不均匀性。控制钢水成分w（C）〉0.185%、w（Mn）/w（S）≥55、过热度在25～30℃;保护渣碱度1.17～1.21、黏度0.08～0.10Pa.s、熔化温度1 070～1 090℃;热流密度在2.3～2.5MW/m2时,有利于减少J55钢薄板坯表面纵裂。     

工艺参数对连续定向凝固Cu-12%Al线材表面质量、组织和性能的影响

采用真空熔炼、氩气保护下拉式连续定向凝固方法制备了直径为6mm的Cu-12%Al(质量分数)合金线材,并研究了结晶器长度、熔体温度和拉坯速度对线材表面质量、组织和力学性能的影响.结果表明:在结晶器长度为20~40mm,熔体温度为1100~1250℃,拉坯速度为10~70mm·min^-1范围内,可以稳定制备出具有单晶或柱状晶组织的线材.缩短结晶器长度、提高熔体温度或拉坯速度均有利于改善线材表面质量;降低熔体温度、增加结晶器长度或提高拉坯速度连铸有利于获得连续柱状晶组织.当结晶器长度为30mm,熔体温度为1100~1150℃,拉坯速度为10~70mm·min^-1时,线材横截面晶粒尺寸随拉坯速度的增加先减小而后增加.在结晶器长度30mm,熔体温度1150℃,拉坯速度30mm·min^-1条件下制备的连续柱状晶组织线材,其延伸率可达25.7%.     

Review of Traumatic stress: The effects of overwhelming experience on mind, body, and society.

Reviews the book, Traumatic stress: The effects of overwhelming experience on mind, body, and society edited by Bessel A. van der Kolk, Alexander C. McFarland, and Lars Weisaeth (see record 1996-98017-000). According to the reviewer, this book has, no doubt, been long awaited by professionals working in the field of traumatic stress. On the whole, it should be welcomed by psychiatrists. It leaves little reservation that, for the guiding interests of psychology, practitioners and researchers will need to look elsewhere. Although acclaimed on the flyleaf as "the gold standard reference," this book, however, falls far short of that mark, and it is bewildering and disappointing that this ambitious, extensive volume comes to so little in a field requiring lucid and advanced theoretical and empirical contributions. The book's purpose is a synthesis of what has been learned over the past 20 years about the effects of trauma, using a biopsychosocial framework. The emphasis throughout is on psychobiology and intrapersonal psychology, attention to the latter at times appearing almost quaint. The book is more properly read as a synthesis of some of the prevailing viewpoints expressed within psychiatry. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects on teachers' self-efficacy and job satisfaction: Teacher gender, years of experience, and job stress.

The authors of this study sought to examine the relationships among teachers' years of experience, teacher characteristics (gender and teaching level), three domains of self-efficacy (instructional strategies, classroom management, and student engagement), two types of job stress (workload and classroom stress), and job satisfaction with a sample of 1,430 practicing teachers using factor analysis, item response modeling, systems of equations, and a structural equation model. Teachers' years of experience showed nonlinear relationships with all three self-efficacy factors, increasing from early career to mid-career and then falling afterwards. Female teachers had greater workload stress, greater classroom stress from student behaviors, and lower classroom management self-efficacy. Teachers with greater workload stress had greater classroom management self-efficacy, whereas teachers with greater classroom stress had lower self-efficacy and lower job satisfaction. Those teaching young children (in elementary grades and kindergarten) had higher levels of self-efficacy for classroom management and student engagement. Lastly, teachers with greater classroom management self-efficacy or greater instructional strategies self-efficacy had greater job satisfaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Radiation factor: Effect on the structure and stress state of condensates produced by ion sputtering of Ti-W-B refractory materials

The paper examines the structurization and stress state of ion-plasma condensates of Ti-W-B refractory materials exposed to radiation in deposition. High imbalance is found, which is characteristic of materials condensed with ion bombardment, the mean atomic energy of film-forming particles ranging from several to several tens of electron volts. Models for optimizing the structure and stress state of condensates exposed to radiation to improve their mechanical properties are discussed. __________ Translated from Poroshkovaya Metallurgiya, Vol. 47, No. 1–2 (459), pp. 72–83, 2008.     

Learning how to recover from job stress: Effects of a recovery training program on recovery, recovery-related self-efficacy, and well-being.

This quasi-experimental study evaluated the effects of a recovery training program on recovery experiences (psychological detachment from work, relaxation, mastery experiences, and control during off-job time), recovery-related self-efficacy, and well-being outcomes. The training comprised two sessions held one week apart. Recovery experiences, recovery-related self-efficacy, and well-being outcomes were measured before the training (T1) and one week (T2) and three weeks (T3) after the training. A training group consisting of 48 individuals and a waitlist control group of 47 individuals were compared (N = 95). Analyses of covariance revealed an increase in recovery experiences at T2 and T3 (for mastery only at T2). Recovery-related self-efficacy and sleep quality increased at T2 and T3, perceived stress and state negative affect decreased at T3. No training effects were found for emotional exhaustion. (PsycINFO Database Record (c) 2011 APA, all rights reserved)