Tribocorrosion of Stellite 706 and Tribaloy 400 superalloys

Abstract

Co based superalloys such as Stellites and Tribaloys have been extensively used in many engineering applications owing to their inherent superior corrosion and wear resistance and hot hardness property at elevated temperatures. The combined interaction among wear and corrosion which is known as tribocorrosion often results in a significant increase in material loss especially in aqueous environments. In this study tribocorrosion performance of Stellite 706 and Tribaloy T400 was investigated by electrochemical techniques such as potentiodynamic (anodic polarisation) and open circuit potential (OCP) measurement with three electrode electrochemical cell set-up under sliding contact in 3·5% NaCl solution. The effect of friction on anodic polarisation behaviour of superalloys was studied at different loads of 20 and 80 N. During OCP measurements the frequency was increased from 0·5 to 1·5 Hz by an increment of 0·5 Hz. Thus the effect of frequency on tribocorrosion behaviour of superalloys was determined. Tribaloy 400 exhibited greater performance in potentiodynamic polarisation test. On the other hand, Tribaloy 400 was more affected by corrosive wear in OCP measurements as compared to Stellite 706.     

Temperature effect on the reference frequency of FDR soil moisture sensor

The FDR automatic soil moisture sensor must determine reference frequency in the air and water. Experimental studies show that the water reference frequency is influenced by water temperature. The variation of the reference frequency of the sensor is measured with the change of the water temperature,then analysis the influence of the volume water content measurement of the sensor,analysis found that the error is not more than 3% for the measurement of the volumetric water content of the temperature.     

Method for Detecting Multi-Modal Vibration Characteristics of Landmines

The acoustic vibration characteristics of landmines are investigated by means of modal analysis. According to the mechanical structure of landmines, a certain n...     

New research trends on high-precision time transfer technology

High-precision time transfer plays an important role in the areas of fundamental research and applications. Accompanying w ith the remarkable improvements in the ability of generating and measuring high-accuracy time-frequency signal,seeking for new time-transfer techniques betw een distant clocks w ith much further improved accuracy attracts attentions w orld-w idely. The time-transfer technique based on optical pulses has the highest precision presently,and the further improvement in the accuracy is heavily dependent on the time-domain properties of the pulse as w ell as the sensitivity of the applied measurement on the exchanged pulse. The application of optical frequency comb in time transfer for a precision up to femtosecond level are currently the focus of much interest,and has recently achieved many breakthroughs. Further investigations show that,utilizing quantum techniques,i.e. quantum measurement technique and quantum optical pulse source,can lead to a new limit on the measured timing information. Furthermore,it can be immune from atmospheric parameters,such as pressure,temperature,humidity and so on.Such quantum improvements on time-transfer have a bright prospect in the future applications requiring extremely high-accuracy timing and ranging. The potential achievements w ill form a technical basis for the future realization of sub-femtosecond time transfer system.     

关于密封垫片压缩回复性能名词术语的探讨

密封垫片的压缩回复性是一项十分重要的性能.目前国内对＂回复＂和＂回弹＂两个概念没有很好地区别,以致普遍采用＂回弹率＂这一术语.讨论了＂回弹率＂和＂回复率＂的区别,并建议采用＂回复率＂或＂复原率＂替代＂回弹率＂.     

A novel representation of tandem systems with inter-stage storage applied to on-line system monitoring

One of the goals of operating a tandem manufacturing system with finite inter-stage storage and asynchronous operations is to meet the demand without over-producing, under-producing or carrying large quantities of material in storage. We believe that analysing the operation of such a system on a real-time basis helps achieve this goal. The first step in this real-time analysis would be to quantitatively associate the causes and effects of over-production or under-production as they occur. This requires determining the cumulative effect that the performance that any stage has on the system, based on its history, the current system state and the interrelationships between the stages. This paper proposes a method which first represents uniquely and completely each stage and surrounding storage as an element. While this system, which consists only of this simple type of element functions in exactly the same way as the original one, each element is put into an ideal world for decoupled measurement. Though an element behaves in exactly the same way whether it is in the ideal world or in the real world, the elapsed times in the two worlds since the beginning of production can be different, since the responses (occurrences and durations of the blockings and starvations) of the two worlds can be different. A phase parameter is introduced for each element to represent this difference. Once the formation of the phase parameter of the output element is formulated, quantitative relationships between causes and effects of over-producing or under-producing can be explained as they occur.     

Singularity and workspace analysis of three isoconstrained parallel manipulators with schoenflies motion

This paper presents the analysis of three parallel manipulators with Schoenflies-motion. Each parallel manipulator possesses two limbs in structure and the end-effector has three DOFs (degree of freedom) in the translational motion and one DOF in rotational motion about a given direction axis with respect to the world coordinate system. The three isoconstrained parallel manipulators have the structures denoted as CuuUwHw-//-CvvUwHw, CuRuuUhw-//-CvRvvUhw and CuPuUhw-//- CvPvUhw. The kinematic equations are first introduced for each manipulator. Then, Jacobian matrix, singularity, workspace, and performance index for each mechanism are subsequently derived and analysed for the first time. The results can be helpful for the engineers to evaluate such kind of parallel robots for possible application in industry where pick-and-place motion is required.     

Portable Electromagnetic-Acoustic Thickness Meters (EMAT)

Two varieties of contactless electromagnetic-acoustic portable thickness meters with autonomous power supply, created on the basis of up-to-date digital technologies, are described. The instruments implement a new highly efficient design of magnetic field concentrator developed on the basis of new magnetic materials. The -- thickness meter is equipped with a powerful microprocessor-based data processing system, which expands the capabilities of the instrument. The -100 thickness meter is a small-size and small-weight instrument. The main advantage of both instruments is that they can be operated on corroded untreated surfaces without the use of a contact fluid. Both instruments are suitable for testing through coatings of considerable thickness (up to 2 mm) and can be operated under workshop and field conditions.     

Error Corrections in a Sampling Sliding Along a Pulse Envelope Based on Decoding Tables

Code combinations of 2 ⁿ symbols +1 and –1 suggested for identification of characteristic features leading edge, trailing edge, maximum, minimum, horizontal portion, start of leading edge, end of leading edge, start of trailing edge, and end of trailing edge in a binary-code envelope of a pulse measured by an eddy-current transducer (ECT) scanning a tested surface generate a group code. This group code ensures for four levels of noise immunity the maximal likelihood in identification of reference sequences distorted by noise. The structure of a product code, which is also generated by the reference fragments, results in a higher capability of correcting for errors in moving samplings of signal envelopes, in particular, it reduces the degree of uncertainty in identification of the most important features of ECT pulses. The paper suggests simple decoding algorithms and regular logical structures that provide a high efficiency of the procedure eliminating errors in binary sequences of coded envelopes.     

Single-Electron Characteristics of a ФЭУ-184U Photomultiplier Tube

Single-electron and time characteristics of a -184U photomultiplier tube with a uviol window are presented. The -184U single-electron resolution can reach a value of 63–64%, and, in case of single-electron light-striking of the photocathode, the photoelectron transit time distribution (full width at half maximum) is 6 ns.     

Detection of the Increment of an Instantaneous Phase in a Long-Base Laser Meter of Small Vibrations

A phase meter for processing signals of a laser meter of small displacements and vibrations at long base distances is described. Vibrations of objects are transformed into small increments of a signal phase at an RF carrier, which are detected by the phase meter and are outputted as signals proportional to microvibrations in the acoustic range. At a given carrier frequency f _c = 10.7 MHz, vibrations are detected within a band f = 3 kHz. Such vibrations produce phase fluctuations of 10^–42, which correspond to magnitudes of 1 nm for a laser wavelength 10 m.     

从e-商务到e-工厂的NW/IT变革 e-时代的10年发展

从1993年美国国防部DARPANet、能源部BITNet、国家自然科学基金会NFSNet搭桥并网,1994年解密为商用internet,到装上欧洲19国CERN开发的WWW,开展全球e-m、e-a、e-3b业务,形成“信息高速公路”上的“新经济”和“知识经济”。这“e-时代”10年发展的趋势是:“e-商务”经由e-efg落实到“透明工厂”,再发展到“e-工厂”,应证了马克思的经典论点“工具的革新是生产力中最重要的”,美国人的现代观点“硅谷是美国的工艺心脏”。