Preparation technology of carbide steels

Kinetic dependences of the average particle size of carbides and steels during milling in an attritor are investigated. The volume content of various fractions in the powders under study is established. The technology of preparing the powder charges for the acquisition of carbide steels 40X2-B₄C, P6M5K5-TiC, and X18H15-Cr₃C₂ used in the production of machine building wares operating under conditions of increased wear, high temperatures, and corrosion media is presented.     

A review of the development and application of microalloyed medium carbon steels

Microalloyed medium-carbon steels with ferrite-pearlite microstructure were developed in the FRG in early 1972, with the primary aim of saving the cost of heat treatment. A steel with roughly 0.47% C, 0.75% Mn, 0.060% S and 0.1 % V was first used for crankshafts in cars manufactured by one of the largest European automobile companies. The effect of microalloying elements such as vanadium and niobium (niobium instead of columbium is used in this paper) in these steels and their dependence on the cooling rate from drop-forging temperatures is reviewed. Although niobium is more effective than vanadium, it leads to problems while manufacturing these steels with ~0.47% C, due to the high solution temperature of the niobium precipitates, so that preference has been given to vanadium. Further development work carried out to improve the ductility of these steels is reported. Steel compositions, which could make these steels applicable for various automobile and other engineering components, are presented.     

Cracking resistance and strength of carbide steels

Conclusions The carbide steels with binders of austenitic or austenitic-martensitic steels have high cracking resistance which is not inferior to that of the tungsten carbide hard alloys (at the same volume content of the metallic phase). This can be explained by high ductility of the binder of these materials.There is a relationship between cracking resistance and certain properties of the carbide steels, such as hardness, proof stress, and the limiting plastic strain in compression: a reduction of HV, _0.1, and an increase of ₁ are accompanied by an increase of K_1c. Consequently, it is possible to evaluate the cracking resistance on the basis of these available and relatively easy to determine mechanical properties.Translated from Poroshhkovaya Metallurgiya, No. 1(325), pp. 90–94, January, 1990.     

Indices of the serviceability of carbide steels

Translated from Poroshkovaya Metallurgiya, No. 2(326), pp. 48–53, February, 1990.     

几种典型双相不锈钢组织及性能特点及其对加工过程的影响

本文选择几种典型的双相不锈钢:S32707、S32750、S32205、S31803,在其工件上取样,采取了不同的热处理、热加工和热穿孔以及适当调整化学成分等试验方法,比较和研究了组织和性能特点及其对加工过程的影响。结果表明:两相比例和σ相的析出情况与热穿孔温度和冷变形的退火、固溶处理温度密切相关,S32707的二次相的析出速度和析出量远超于其他双相不锈钢。适当降低Cr、N含量,提高Mo含量,合理控制加热速度,终乳(锻)温度,并注意回炉加热和圆管坯中心钻孔的影响,可提高热加工塑性,防止开裂。试验中的S32707成品无缝管满足相关标准的要求。     

Methods of production and properties of sintered stainless steels for machine components — A review

Powder Metallurgy and Metal Ceramics -     

Recent development in upconversion nanoparticles and their application in optogenetics: A review

Ion channels present in the plasma membrane are responsible for integration and propagation of electric signals, which transmit information in nerve cells. Malfunction of these ion channels leads to many neurological diseases. Recently, optogenetic technology has gained a lot of attention for the manipulation of neuronal circuits. Optogenetics is a neuromodulation approach that has been developed to control neuronal functions and activities using light. The lanthanide-doped upconversion nanoparticles (UCNPs) absorb low energy photons in near-infrared (NIR) window and emit high energy photons in the visible spectrum region via nonlinear processes. In the last few decades, UCNPs have gained great attention in various bio-medical applications such as bio-imaging, drug delivery and optogenetics. The near-infrared illumination is considered more suitable for optogenetics application, due to its lower degree of light attenuation and higher tissue penetration compared to visible light. Therefore, UCNPs have been considered as the new promising candidates for optogenetics applications. Upconversion nanoparticle-mediated optogenetic systems provide a great opportunity to manipulate the ion channel in deep tissue. Herein, we summarize the upconversion photoluminescence in lanthanide doped nanomaterials and its mechanisms and several approaches adopted to tune emission color or enhance upconversion efficiency. Recent advances of lanthanide-doped UCNPs design strategy and their mechanism are reviewed. Then, we discuss the neural circuitry modulation using upconversion nanoparticles mediated optogenetics. Moreover, the future perspectives towards optogenetics are also included.     

The kinetics of carbide precipitation in silicon-aluminum steels

The kinetics of carbide precipitation in a fully processed 2.3 wt Pct silicon, 0.66 wt Pct aluminum electrical steel with carbon contents of 0.005 to 0.016 wt Pct were investigated over the temperature range from 150 to 760 °C and times from 30 seconds to 240 hours. The size, morphology, and distribution of the carbide phases, as functions of aging time and temperature, were determined by optical and transmission electron microscopy. The 1.5T core loss was also evaluated and correlated with the changes in precipitation. Distinct C curves were observed for the formation of grain-boundary cementite at temperatures above 350 °C and a transition carbide ({100} _α habit plane) at temperatures below 350 °C. Grain-boundary cementite had a relatively small effect on core loss. The large increases in core loss that accompanied transition carbide precipitation peaked at specific aging temperatures depending on the carbon content of the steel. Once a transition carbide dispersion was initially established at a given aging temperature, particle coarsening and core loss changes were generally insensitive to aging time. The influence of a combined addition of silicon and aluminum on the solubility of cementite and the transition carbide in iron was estimated and discussed. This paper is based on a presentation made at the symposium “Physical Metallurgy of Electrical Steels” held at the 1985 annual AIME meeting in New York on February 24–28, 1985, under the auspices of the TMS Ferrous Metallurgy Committee.     

Diffusion interaction of vanadium carbide with powdered steels

Conclusions The processes of diffusion interaction of vanadium carbides with cast and powdered steels are largely analogous. Differences are mainly due to unequal diffusional mobility of the components in cast and powdered materials.In cast and powdered steels equal boundary concentration of vanadium are established on the boundary with the carbides, and these concentrations are determined by the carbon content of the steel and by the temperature.The interdiffusion coefficient in ferrite does not depend on the carbon content, and it is the same for cast and powdered steels. The interdiffusion coefficient in austenite increases with increasing carbon content, and it is noticeably larger in powdered steels than in cast steels.The activation energy of interdiffusion in the austenite of powdered steels (220–230 kJ/mole) is noticeably lower than in cast steels (260–270 kJ/mole); this is due to the substantial contribution of the processes of surface diffusion to the overall mass transfer in porous materials.Translated from Poroshkovaya Metallurgiya, No. 11(323), pp. 40–45, November, 1989.     

浅谈耐高温用铁素体型钢铁材料

耐高温材料的开发和材料高温下安全服役的实现一直是材料领域关注的热点问题。简要阐述了钢铁材料强度性能随温度变化的一般规律、材料强度在高温下的主要损失机理,并详细介绍了几种代表性的耐高温用途的铁素体型钢铁材料的合金化思想和强化机制,可为今后针对其他应用条件,开发新型耐高温钢铁材料、改善现有材料耐高温性能提供技术经验借鉴。     

Electric-spark alloying of steels with chromium carbide base alloys

Conclusions It is shown that, of the Cr₃C₂-Fe cermets investigated, KKhZh-50 alloy is the best alloying electrode material. Alloying should be performed under soft conditions (E_pulse ^–2 J). The quality of the reinforced layer depends on the pulse energy and the base and electrode materials. The continuity of the layer increases and its surface roughness and thickness decrease with increasing pulse energy. Anode erosion and alloyed layer formation are affected by the secondary structure on the electron surface. For KKhZh-50 alloy its formation decreases anode erosion and the cathode weight gain, while for KKhNF-15 alloy, by contrast, it increases them. It is proposed that, to increase the corrosion resistance of such coatings (by about two orders), 65G steel should be alloyed in two stages, first with KKhZh-50 cermet and then with nickel.Translated from Poroshkovaya Metallurgiya, No, 4(304), pp. 1–6, April, 1988.     

Liquid-phase sintering of TiN-enriched T15-grade high-speed steels and their mechanical properties

The present investigation is an attempt to develop composites based on high-speed steel through liquid-phase sintering route using a powder metallurgical technique. Water-atomised annealed T15-grade HSS powder, lubricant and various mass percents of TiN (0–8%) were blended and axially compacted into green pellets at 850 MPa at room temperature. During sintering studies carried out in vacuum (10^?2 torr), optimum temperature for full densification was determined for each composition. Only full dense sintered samples (density ≥98% theoretical) were selected for further heat treatment and the evaluation of mechanical properties. Mechanical properties like hardness, transverse rupture strength and hot compressive yield strength were evaluated. Both qualitative and quantitative metallographic studies were carried out and chemical analysis of various phases in sintered as well as heat-treated composites were determined using SEM-EDX. The results confirm that fully dense composites containing up to 2% TiN exhibit equivalent mechanical properties, although some differences in service behaviour e.g. wear resistance are to be expected.     

Production of boron-containing powder steels using master alloys and boron carbide

Powder Metallurgy and Metal Ceramics - The properties of boron-containing structural powder steels produced using master alloys and boron carbide are examined. It is established that sintered and...     

Tobacco, alcohol, and caffeine use: A review of their interrelationships.

Reviews observational and survey studies on the simultaneous use of 2 or more of the following substances: tobacco, alcohol, or caffeine. Evidence to date indicates that, among each of the 3 possible pairs of relationships of these 3 substances, alcohol and tobacco use and tobacco and caffeine use are moderately to strongly related, and caffeine and alcohol use weakly related. These studies included the use of tobacco and alcohol by adolescents and the use of cigarettes by alcoholics. No studies examined the concurrent use of all 3 substances. The need for improved methods of assessing substance use and research examining health-risk behaviors as interrelated clusters is emphasized, and mechanisms that might account for these interrelationships are discussed. Although there are no general theoretical models that adequately account for these interrelationships, the role of several specific pharmacological or behavioral mechanisms as well as generalized individual difference factors may be postulated. (89 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Titanium carbide-based carbide steels made of chips of titanium alloys

Properties and microstructure of carbide steels produced on the basis of titanium carbide are studied. Powdered TiC was obtained from chip wastes of the titanium alloys VT1-0, VT20, VT3-1, VT25, VT5-1, and OT4-1 in three ways: nitridingcarbidizing, double carbidizing, and oxidizing-carbidizing. It has been determined that presence of nitrogen deteriorates the properties of carbide steels. The high values of strength and hardness obtained by oxidizing-carbidizing and double carbidizing of VT5-1 alloy chips testify to the advisability of using such chips for producing carbide steels.Translated from Poroshkovaya Metallurgiya, No. 10, pp. 78–82, October, 1992.     

A review of failure of sintered steels: fractography of static and dynamic crack nucleation,coalescence, growth and propagation

The failure of sintered steels differs from the behaviour of wrought steels because of factors such as porosity, remnants of previous particle surfaces and generally more complex microstructures. All these factors influence initiation, growth and propagation of microcracks when the sintered microstructure is mechanically loaded. Fracture paths and fracture resistance are shown to be related to details of the microstructures comprising ferrite, austenite, bainite, martensite, pores and weak interfaces. All these have characteristic fracture resistance properties resulting in, frequently combinations of, dimple rupture, cleavage, intergranular and interparticle failure micromechanisms. Results are presented of systematic studies, enabling identification of relevant stresses, in static and dynamic three-point loading, as the cracking process progresses. In static loading, microcracking has been detected in some steels below the macroscopic yield stress and in the first 100 cycles in fatigue. Microcracks nucleate, grow and coalesce, in a step-wise manner, before achieving a catastrophic size – for which conventional fracture mechanics holds. Thus, application of Paris-type analysis to Stage II fatigue is therefore inappropriate. The review focuses on failure micromechanisms and interpretation of fracture surface composition of sintered steels, particularly of those based on Distaloy AE and Astaloy CrL powders. The relationships between microstructure and mechanical properties are discussed.