Search results

This paper aims to investigate the influence of slurry concentration on the erosion behavior of AISI 5117 steel and high-chromium white cast iron by using a whirling-arm rig. In this study, the slurry erosion mechanism with particle concentration has been studied.

The tests were carried out with particle concentrations in the range of 1-7 Wt.%, and the impact velocity of slurry stream was 15 m/s. Silica sand with a nominal size range of 500-710 µm was used as an erodent. The study revealed that the failure mode was independent of concentration.

The results showed that the erosion rate decreases with the increase in particle concentration and the variation in the reduction depends on the material. It was found that the variation of fractal dimension calculated from slope of linearized power spectral density of eroded surface image for different concentrations can be used to characterize the slurry erosion intensity in a similar manner to the erosion rate. It was also found that the variation of fractal dimension versus concentration of sand has a general trend that does not depend on magnification factor.

Using the gravitational measurement and image analysis, the variation of the wear with slurry concentration has been analyzed to investigate the implicated mechanisms of erosion during the process.

This paper aims to demonstrate the effect of varying chromium content on the wear behavior of white cast iron, to study the interaction relationship between cementite and pearlite in white cast iron, while estimating their contribution rate in abrasive wear.

To study interaction of cementite-pearlite of white cast irons with different chromium content in three-body abrasive wear, three kinds of chromium white cast iron, bulk single-phase cementite, pure pearlite samples and the white cast iron (WCI), were prepared using the melting and casting technique. The so-called pure pearlite samples have the same chemical composition, microstructure and properties as the pearlite matrix in white cast iron.

Results indicated that the interaction has a negative value. Its absolute value decreased with increasing chromium addition. Meanwhile, a high load resulted in an increased interaction value. The contribution rate of cementite to interaction, which was higher than that of pearlite, increased with increasing chromium addition. This indicated cementite was a main phase. Besides, the reductive size of abrasive has a significant effect on the contribution rate at the high load. These prominent cementite occurred fracture, when small size abrasive indented the matrix. These result in the absence of a protective effect of cementite during wear process. Eventually, the contribution rate of cementite decreased significantly.

This paper demonstrates the effect of varying chromium content on wear behavior of white cast iron, to study the interaction relationship between cementite and pearlite in white cast iron while estimating their contribution rate in abrasive wear.

The directional solidification Fe-B alloy was prepared. The microstructures and three-body abrasive wear behaviors of directional solidification alloy were investigated.

Fe-B alloy was melted in medium frequency induction furnace. The hardness was measured on HRS-150 Rockwell-hardness tester and HXD-1000TMC tester. The wear characteristic of the alloy was examined with a block-on-ring geometry. The worn surface of the alloy was investigated by scanning electron microscopy and laser scanning microscopy.

The wear weight loss and worn surface roughness increase with the increasing contact load in wear tests. When the worn surface is perpendicular to the boride growth direction, the highest hardness plane of the boride can resist abrasive effectively under the surrounding and supporting of the martensite matrix.

The relation between boride growth direction and wear direction will cause different boride breaking tendency and wear weight loss.

The relationship between Cr/C and properties of Fe‐C‐Cr high chromium white irons was studied by calculating the valence electron structure of austenite of Fe‐C‐Cr high chromium white irons with the empirical electron theory of solids and molecules (EET) and the equilibrium phase diagram of Fe‐C‐Cr system. Results show that the C‐Cr bond is the strongest bond of all bonds in alloying austenite in Fe‐C‐Cr high chromium white irons of industrial application and, thereby, causes partial aggregation of C‐Cr atomic groups. The weight of partial aggregation of C‐Cr atomic groups would be increased greatly and more austenite would be reserved to room temperature when Cr/>6. The Fe‐CCr high chromium white irons achieve best mechanical property when Cr/C=5.5‐6.5.

131A Aluminium Alloy Sand or Die Castings (suitable for Pistons, etc.).

WEAR is one of the major ways by which a material part ceases to be useful, others are corrosion, obsolescence and breakage. It is the consequence of relative motion and in industrial plant and equipment it has always been accepted as inevitable that it should lead to heavy expenditure for maintenance and replacement. Historically, wear is a well established fact, yet our knowledge of the technology is extremely limited. It has become a way of life that we compensate for wear when it no longer can be tolerated, yet need this be so? This article examines the problem, and primarily from the unlubricated point of view, describes the various types of wear and the way material selection or modification can be used to limit wear.

The purpose of this paper is to study the microstructure and the high-temperature tribology behavior of a high-speed steel (HSS) roller material with boron as the main alloy element under different heat treatments, aiming to provide some theoretical references for its engineering application.

The samples of high boron HSS were quenched at 900°C, 1,000°C, 1,050°C and 1,150°C. The microstructure, composition and phase composition of this new HSS were analyzed by OM, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffractometer. The surface hardness and the tribology behavior under high temperature were measured by Rockwell hardness tester and the high-temperature friction and wear tester. The wear morphology was observed by SEM.

The high-temperature friction coefficient and the relative wear rate of the high boron HSS decrease first, then increase with the rise of the quenching temperature. When the quenching temperature is 1,050°C, both the friction coefficient (0.425) and the relative wear rate (79 per cent) are the smallest. Under the high-temperature friction environment, the high boron HSS mainly includes oxidation wear, adhesive wear and abrasive wear. The effect of abrasive wear is weakened gradually with the rise of the quenching temperature, and the high-temperature wear resistance is improved significantly. Compared with the traditional roll materials, the service life of the new high boron HSS is greatly improved. It is an ideal substitute product for the high chromium cast iron roll.

The boron element replaces other precious metals in high boron HSS, which has the advantage of low production cost, and it has a wide application in the field of roll materials. In this paper, the microstructure, the transformation of hard phases and the high-temperature tribology behavior of this new high boron HSS under different heat treatments were studied, aiming to provide some theoretical references for its engineering application.

NEARLY twenty years have passed since the author had the pleasure of giving a paper on the same subject to this Society. Progress in the meantime as regards the means and art of flying has been not only sustained, but rapid, as is brought out by the simple facts contained in Table I. The amazing technology is well represented by the De Havilland Comet, which develops 460 h.p. with a weight ratio of 12 lb. per h.p. It therefore becomes interesting and perhaps useful to determine the extent to which metallurgy has contributed and is contributing.

THE use of metals at temperatures in excess of 1,200 deg. F. and up to temperatures in the vicinity of their melting points is a challenging and fascinating portion of the fight to pass the heat barrier in the design and performance of aircraft and their power plants. The materials available for service in this temperature range are restricted. The considerations of designing structural components involve many more problems than the old criteria of strength to weight ratio and fabrication costs. Such properties as thermal expansion, heat conductivity, surface emissivity and scaling resistance are as important in determining which metal should be used for a given application as are the various measurements of strength heretofore the primary considerations in material selection.

Introduction There are many elements in an alloyed combination with iron; some are present as ‘impurities’ and there are those which are added to confer specific properties to the material to improve either the mechanical or corrosion resisting properties, or both.