Wear of magnetic materials and audio heads sliding against magnetic tapes

The friction and wear of various materials and audio heads sliding against magnetic tapes were studied. Magnetic materials such as Permalloy, Sendust and hot-pressed ferrite (HPF) and some other non-magnetic materials were used as material specimens. Three types of audio heads for cassette tape recorders were used as the head specimens. Their magnetic cores were made from ordinary Permalloy, hard Permalloy and HPF. An experiment using a conical diamond slider was carried out to study the wear resistance of various materials. The specific wear rates of the various material specimens and components of the heads such as the core, shield plate and epoxy resin were measured using the Knoop indentation technique. Wear did not occur uniformly over the surfaces of the Permalloy heads. This irregular wear was examined in detail and its origin is discussed. The specific wear rates of Permalloy and HPF are of the order of 10^?5 mm³ N^?1 m^?1 and 10^?6 mm³ N^?1 m^?1 respectively and that of epoxy resin is of the order of 10^?4 – 10^?5 mm³ N^?1 m^?1. The coefficient of friction of an HPF head is about 0.3, while that of both types of Permalloy head is about 0.7. It is concluded that the mechanism of wear by magnetic tape is not entirely due to the abrasive action of the magnetic powder in the tape but is also partially adhesive in nature.     

Some observations on the wear of aluminium rubbing on steel

Wear tests on high pressure counterformal contacts between an aluminium alloy and a low carbon steel produced different regimes of wear depending on specimen geometry and whether the aluminium specimen was disposed as the stationary specimen or the counterface. Oxidative wear was maintained at high levels of unit load (200 MN m^?2) provided that the surfaces were not subjected to large-scale plastic flow. Wear rates were greatly increased when the amount of aluminium transfer onto the steel surface was substantial, and under these circumstances evidence of back transfer was observed.     

Finish Machining of Nickel-Base Inconel 718 Alloy with Coated Carbide Tool under Conventional and High-Pressure Coolant Supplies

Single-point turning of Inconel 718 alloy with commercially available Physical Vapour Deposition (PVD)-coated carbide tools under conventional and high-pressure coolant supplies up to 20.3 MPa was carried out. Tool life, surface roughness (Ra), tool wear, and component forces were recorded and analyzed. The test results show that acceptable surface finish and improved tool life can be achieved when machining Inconel 718 with high coolant pressures. The highest improvement in tool life (349%) was achieved when machining with 11 MPa coolant supply pressure at higher speed conditions of 60 m · min^?1. Machining with coolant pressures in excess of 11 MPa at cutting speeds up to 40 m · min^?1 lowered tool life more than when machining under conventional coolant flow at a feed rate of 0.1 mm · rev^?1. This suggests that there is a critical coolant pressure under which the cutting tools performed better under high-pressure coolant supplies.

Cutting forces increased with increasing cutting speed due probably to reactive forces introduced by the high-pressure coolant jet. Tool wear/wear rate increased gradually with prolonged machining with high coolant pressures due to improved coolant access to the cutting interface, hence lowering cutting temperature. Nose wear was the dominant tool failure mode when machining with coated carbide tools due probably to a reduction in the chip-tool and tool-workpiece contact length/area.     

Abrasive wear behaviour of sintered composite austenitic stainless steels having γ-Fe and M23C6 phases

Abstract

Using powder metallurgy, composites of austenitic stainless steel were produced along with unreinforced stainless steel mixed with titanium, cobalt and molybdenum particles. Wear resistance of the materials was measured by a two body pin on disc wear tester. SiC abrasive papers of 80 and 220 mesh sizes were used as abrasive media. Wear tests were performed under loads of 10, 20 and 30 N at room temperature. The abrasive wear measurements showed that the softer, unreinforced austenitic stainless steel exhibited higher mass loss than the composites. Furthermore, the abrasive wear resistance of the reinforced austenitic stainless steel composites increased with increasing FeTi, FeMo, or Co volume content. In addition, the wear rate against the 80 grade SiC abrasive paper increased more than against the 220 grade SiC abrasive paper.     

Sliding wear behavior of electron beam surface-melted 0–2 tool steel

Studies were carried out on the dry sliding wear behavior of electron beam melted surface layers on a type 0–2 tool steel and on annealed and conventionally hardened 0–2 steel specimens for comparison. Wear tests were conducted in a flowing argon atmosphere at a sliding speed of 20 cm s^?1 and a load of 10 N against a 52100 bearing steel ring. Wear surface morphology was studied along with subsurface structure using optical and electron microscopy methods. The study concentrated on the wear of this steel after different processing treatments. Electron beam surface melting and subsequent rapid solidification in situ of the steel produced a highly refined martensitic microstructure having higher hardness values and better wear resistance than obtained using conventional quench hardening of that steel. Carbide distribution and martensite phase morphology were affected by this surface melting process; those microstructural characteristics influenced the wear behavior. Variations in electron beam power and surface speed during melting were explored in terms of their effect on the resulting surface layer. The wear test system used was computer interfaced and controlled, permitting continuous measurements of wear depth and friction force.     

Correlation of wear with oxidation of carbon-carbon composites

The wear characteristics of carbon-carbon composites for aircraft brake materials were investigated using an inertial dynamometer. Wear rates were measured in terms of weight loss and thickness reduction.The wear rates in terms of weight loss are always greater than those in terms of thickness reduction over a wide range of braking conditions. This difference agrees with previous work carried out under a normal braking condition and, as before, is attributed to the oxidation of carbon beneath the porous friction surfaces. Good agreement was obtained between the activation energies for the oxidation of carbon (29 kcal mol^?1) and for material loss on non-friction surfaces (27 kcal mol^?1). Such good agreement suggests that the rate-controlling step for oxidative weight loss is the diffusion of oxygen through pores.     

Tribological evaluation of oil pump relief valve coatings compatible with an aluminum oil pump body

Wear can cause automotive relief valves to jam. In order to evaluate and screen candidate coatings for oil pump relief valves for reduction of aluminum pump cylinder bore wear and wear-related sticking, a laboratory reciprocating wear test using production parts has been developed. The coatings on valves include impinged and physical vapor deposited (PVD)-coated molybdenum disulfides, electroplated nickel–phosphorous with polytetrafluoroethylene (Ni–PTFE), electroplated bronze, and electroplated nickel–phosphorous–boron nitride (Ni–P–BN).

The test results showed that the electroplated bronze coating demonstrated the best wear resistance against 380 aluminum pump bores while Ni–PTFE ranked second, PVD-coated MoS₂ third, and Ni–P–BN ranked last. It was observed that the electroplated bronze coating showed only mild oxidative or abrasive wear after 20 h wear test. The Ni–P–BN coating gave the worst wear resistance due to severe abrasive wear, surface scoring, and coating abrasion during the wear test. The major wear mechanisms for valve bore/relief valve can be classified at different levels from mild wear (oxidative wear or surface delamination) to abrasive wear (scoring, scuffing, and ploughing). This paper also reviewed the rooted wear mechanisms of production pump relief valves against aluminum bores based on metallographic observations of worn surfaces after field tests. This tribological investigation of valve coatings has provided insights into the fundamental wear mechanisms which depend on the compatibility of two sliding materials, protective coating composition, hard particle content, and surface interaction. The information will be useful in preventing oil pump relief valves from jamming.     

Wear Measurement and Assessment of Explanted Cross-Linked PE Acetabular Cups Using a CMM

Wear has been considered the main limiting factor in the longevity of hip replacements. Wear analysis is thus essential for determining wear-related failure mechanisms and prediction of wear, which will consequently enable biomedical engineers to improve the design, material, and service life of the bearing components. This article presents wear measurement and assessment of the explanted conventional cross-linked polyethylene (XPE) and second-generation highly cross-linked polyethylene cups (X3) using a coordinate measuring machine (CMM). An expanded uncertainty analysis was performed to assess the performance of wear measurement. Wear measurement using the CMM method was validated with the gravimetric technique. The normalized error between volumetric wear measurement of the CMM method and that of the gravimetric technique was estimated to be always less than 1, suggesting that the CMM method applied to explanted hip wear measurements under the specific conditions was accurate and reliable. The approach to CMM measurement with uncertainty analysis was shown not only to locate 3D wear scar and wear direction but also to accurately quantify linear and volumetric wear with a maximum volumetric uncertainty of ±3.15 mm³ (95% confidence level). It is shown that identifying the key uncertainty components involved in the measurement process including validation, which contributes to an overall expanded uncertainty budget, is crucial to improve the confidence and the reliability of hip wear measurement results using a CMM.     

停车密封在大亚湾核电站反应堆冷却剂泵的应用可行性探讨

介绍了大亚湾900MW压水堆核电站反应堆冷却剂泵的机械密封结构,针对福岛事故后,为了提高反应堆冷却剂泵的应对事故能力,重点介绍了目前国外应用比较广泛的两种停车密封结构形式,以及探讨其在国内核电站主泵应用的可行性.     

Can cobalt levels estimate in-vivo wear of metal-on-metal bearings used in hip arthroplasty?

High levels of cobalt and chromium ions are detected in the blood and urine of patients with metal-on-metal (MoM) hip replacement. These elements are released as a result of wear at the bearing surfaces. Wear rates depend on a multitude of factors, which include the bearing geometry, carbon content, manufacturing processes, lubrication, speed and direction of sliding of the surfaces, pattern of loading, and orientation of the components. In-vivo wear of MoM bearings cannot be reliably measured on X-rays because no distinction can be made between the bearing surfaces. Hip simulator studies have shown that wear rates are higher during the initial bedding-in phase and subsequently drop to very low levels. Accordingly, metal ion levels would be expected to decrease with the use of the bearing, measured as implantation time following surgery. However, several clinical studies have found that metal ion levels either gradually rise or fluctuate instead of decreasing to lower levels. Moreover, hip simulator studies predict that large-diameter bearings have lower wear rates than small-diameter bearings. In clinical studies, however, metal levels in patients with large-diameter bearings are unexpectedly higher than those in patients with small-diameter bearings. As a consequence, high cobalt ion levels in patients do not necessarily imply that their MoM bearings produce much wear debris at the time that their levels were measured; it may simply be due to accumulation of wear debris from the preceding time. Exercise-related cobalt rise may overcome this limitation and give a better assessment of the current wear status of a MoM bearing surface than a measure of cobalt levels only.     

Influence evaluation of loading conditions during pressurized thermal shock transients based on thermal-hydraulics and structural analyses

The thermal hydraulic (TH) behavior of coolant water is a key factor in the structural integrity assessments on reactor pressure vessels (RPVs) of pressurized water reactors (PWRs) under pressurized thermal shock (PTS) events, because the TH behavior may affect the loading conditions in the assessment. From the viewpoint of TH behavior, configuration of plant equipment and their dimensions, and operator action time considerably influence various parameters, such as the temperature and flow rate of coolant water and inner pressure. In this study, to investigate the influence of the operator action time on TH behavior during a PTS event, we developed an analysis model for a typical Japanese PWR plant, including the RPV and the main components of both primary and secondary systems, and performed TH analyses by using a system analysis code called RELAP5. We applied two different operator action times based on the Japanese and the United States (US) rules: Operators may act after 10 min (Japanese rules) and 30 min (the US rules) after the occurrence of PTS events. Based on the results of TH analysis with different operator action times, we also performed structural analyses for evaluating thermal-stress distributions in the RPV during PTS events as loading conditions in the structural integrity assessment. From the analysis results, it was clarified that differences in operator action times significantly affect TH behavior and loading conditions, as the Japanese rule may lead to lower stresses than that under the US rule because an earlier operator action caused lower pressure in the RPV.     

Effect of VC and (Ta,Nb)C on wear of WC–10Co based cemented carbides

Abstract

WC–Co cemented carbides, including small angular tungsten carbides particles, are used extensively to improve wear resistance. Some additives can affect mechanical and wear properties of these materials. In this study, the effect of VC and (Ta, Nb)C content on wear of WC–10Co were considered. The tests were performed at normal load of 230 N and sliding distance of 800 m up to 3200 m. Wear tests were carried out using dry sand/rubber wheel apparatus. Wear rate, standard and modified wear coefficients were calculated. The microstructures of prepared specimens were examined by optical microscopy. The morphological analysis of the worn surfaces was made by SEM. The results show that VC content has more effect than (Ta, Nb)C content on wear behaviour. Wear mechanism is different in the specimens, but removal of cobalt rich phase and fracture of carbide grains is clear in all of specimens. Abrasive wear is prevailing in all specimens.     

The Wear of Electrodeposited Gold

The wear and friction of pure gold and gold alloy electrodeposits were determined. These platings are widely used in sliding electric contacts and include golds hardened with silver, cadmium, nickel, cobalt, or cobalt and indium. In preliminary work, the microstructures, hardnesses, crystallographic orientations of the surface, and topographies of the golds were examined; these properties vary widely, and relationships among them are discussed. Sliding was with thick deposits to eliminate effects of substrate. The experimental method involved repeat-pass unidirectional sliding at 100g in a rider-flat apparatus with plated flats against wrought gold or gold-plated riders. Wear and friction are described for both as-plated samples, and to eliminate distinguishing surface textures, with flats abraded to a common roughness.

Wear was found to be related to hardness, topography, and crystallographic orientation. A new result is that prow formation does not occur above a load-dependent critical roughness. For abraded pure gold, the critical value is 25–50 μin. center line average at 100g.

The prow formation wear mechanism dominated sliding in runs of 500 revolutions on a 1-in. diameter track. Exceptional were the very hard golds (about 200 KHN) against soft wrought gold riders (about 50 KHN), in which metal from the rider smeared onto the flat prior to the onset of prow formation. A 1% silver-gold alloy showed unusually high wear, and a 1% cadmium-gold alloy wore relatively, little in the as-plated form. The lowest wear rates were with nickel-or cobalt-hardened golds.

Coefficients of friction of electrodeposits change during running-in. This is related to changes produced by wear in the relative contributions of the adhesion, plowing and roughness components. The friction of very rough or very smooth as-plated gold decreases in repeat-pass sliding as a middle level of roughness is attained.     

The wear behavior of hastelloy B against graphite in a simulated face seal

Wear tests were conducted in a simulated face seal apparatus of Hastelloy B mated against a resin-bonded graphite. The alloy was tested in the solution-annealed (soft) and the aged (hard) conditions in a light wear and a heavy wear regime. The product of the mating pressure and rotational speed was 0.19 × 10⁶Nm^?1s^?1 for the light wear regime and 1.15 × 10⁶Nm^?1s^?1 for the heavy wear regime. The coefficient of friction was 0.07 in the light and about 0.12 in the heavy wear regime; the results were the same for the two conditions of the alloy. The wear rate in the light wear regime was immeasurable. In the heavy wear regime, the wear rate of the graphite was the same against either alloy condition and was about 100 times greater than the wear rate of the alloy. The annealed alloy had a wear rate about twice that of the aged alloy.In the light wear regime, graphite smeared and formed a very adherent coating on the alloy. In the heavy wear regime, the graphite wear surface contained holes and deep grooves; the collected wear debris was mainly graphite flakes and the alloy wear tracks were covered with a rather nonadherent graphite coating. The alloy contained numerous abrasive grooves. The graphite has silicon carbide particles embedded in it which probably improve its wear resistance; these hard particles were responsible for the wear damage to the alloy.     

The influence of reciprocating sliding wear on the oxidation behaviour of Fe-12Cr steel

Medium-chromium ferritic alloys are used extensively in the boiler and core sections of advanced gas cooled reactors (AGRs). It was discovered in the early 1970s, that under certain conditions these alloys could undergo the phenomenon known as breakaway oxidation. In this type of oxidation the rate-limiting step is located at the oxide/metal interface rather than the more usual gas/oxide interface and results in linear oxidation kinetics. It has been shown that repeated removal of oxide layers can expose chromium-depleted metal to the oxidizing gas and promote nucleation of breakaway oxidation. The question has been addressed as to whether high temperature sliding wear processes can also disrupt the surface so as to make the material potentially susceptible to breakaway oxidation.High temperature reciprocating wear tests of Fe-12Cr material in both low and high pressure reactor gas have been caried out. As expected, compact adhesive load-bearing oxide and mixed oxide/metal beds form in wear regions. These contacting features wear at very low rates of less than 10⁻¹⁶m³ (Nm)⁻¹. It has also been demonstrated that preformed oxides wear at sufficiently low rates at high temperature as to preclude the possibility of exposure of the underlying metal to the reactor gas. It is thus unlikely that sliding wear processes will accelerate the tendency for initiation of breakaway oxidation.     

Laboratory wear tests and clinical observations of the penetration of femoral heads into acetabular cups in total replacement hip joints: I: Charnley prostheses with polytetrafluoroethylene acetabular cups

A quarter of a century has now elapsed since the late Professor Sir John Charnley introduced his low friction arthroplasty of the hip based on a stainless steel femoral component and an unfilled polytetrafluoroethylene (PTFE) acetabular cup. The advantages of the very low friction resulting from the use of PTFE and a femoral head of diameter 22 mm were unfortunately outweighed by a very rapid penetration of the femoral head into the acetabular cup. Charnley abandoned the use of PTFE after some 3 years and 300 operations and subsequent measurements revealed a penetration rate of 2.26 mm year^?1. In 1962 he adopted ultrahigh molecular weight polyethylene as the socket material and this material is now used almost exclusively in total replacement joints.In this paper we report further laboratory wear studies of PTFE on stainless steel in disc machines and compare the laboratory wear factors with those deduced from clinical observations. Charnley's clinical penetration rates have been analysed in terms of Paul's loading cycles for steady walking and measurements of the walking activity of elderly patients by Wallbridge and Dowson.It is shown that the wear factor for PTFE and stainless steel is about 3 × 10^?5mm³N^?1m^?1 and that there is excellent agreement between the mean value obtained from a variety of laboratory experiments involving environments of atmospheric air, distilled water, bovine synovial fluid and Ringers' solution with various counterface roughnesses and the wear factors derived from clinical observations.     

核电站用阀门

介绍了压水堆型核电站用阀门的一些基本情况。从核技术的发展，阀门在核电站中的作用等方面，分析了核电站用阀门的特性、参数、用量、品种和结构。     

AP1000蒸汽发生器安装技术

APl000是二环路的1000MWe级压水堆三代核电厂,采用非能动安全设施,与传统的二代压水堆核电技术相比,蒸汽发生器本体特征和核岛内的就位要求均有较大的改进。根据APl000蒸汽发生器自身的特点,并在实践的基础上,对蒸汽发生器的现场安装技术,包括安装准备、现场运输、吊装、核岛安装等进行了介绍和分析,为核电站核蒸汽供应系统主设备的现场运输、吊装和安装提供技术参考。     

Tribology of hydrostatic bearings of coolant pumps of fast neutron reactors with lead coolant

The paper describes the results of developing substantiated designs of hydrostatic bearings for coolant pumps of new-model fast neutron reactors with lead coolant. Analytical assessments of the properties of the high-temperature (450?C550°C) lead coolant, which affect the serviceability of sliding bearings of submerged pumps of reactor circuits, are made. The choice of the hydrostatic bearing as the basic variant in the BREST-300 reactor is shown to be well founded. Experimental and calculation-theoretical studies are carried out for water and liquid heavy metal coolants to determine hydrodynamic and other characteristics of various members of the hydrostatic bearing. The results of the full-scale experiment are compared with the data calculated by the known methods. Two basic optimal variants of the design of the hydrostatic bearing are studied experimentally in water and high-temperature lead melt. The results of the experimental and calculation-theoretical studies are used to refine the available method for the calculation of hydrostatic bearings and develop recommendations for the optimal design schemes of such bearings as applied to conditions of reactors with the lead coolant.     

Transition of the lubricated wear of carbon steel

To study the transition of the lubricated wear of 0.53% C steel in the steady state, wear tests were carried out by rubbing the annular surfaces of two cylindrical test pieces in machine oil with no additives. The ratio of mating areas was varied to approach actual contact conditions. Three regions of variation in the coefficient of friction with contact load were determined. Fatigue wear, characterized by a friction coefficient μ ≈ 0.05 and a specific wear rate ω_s ≈ 0.005 × 10^?6 mm³ N^?1 m^?1, occurs in the first region.A transition from fatigue wear to adhesive wear, with μ ≈ 0.05?0.12 and ω_s ≈ (0.005?0.05) × 10^?6 mm³ N^?1 m^?1, takes place gradually within a specific load range. Finally, adhesive wear predominates above the load level that marks the end of the transition. The same behaviour was analysed through stepwise loading tests. The onset of transition and seizure occurs at constant mean surface temperatures. However, the end of transition is also affected by factors other than temperature. The results are compared with the transitions reported by the International Research Group on Wear of Engineering Materials of the Organization for Economic Cooperation and Development.