On the synergistic effects of abrasion and corrosion during wear

The interactive effects of abrasion and corrosion were studied as a function of abrasive load, corrosion time and the frequency of abrasive and corrosive treatments. The initial rate of corrosion is independent of abrasive load but the percentage contribution to wear of corrosion decreases with increasing abrasive load. It has also been found that increasing the frequency of exposure to abrasion and corrosion increases the wear loss for a constant total amount of abrasion and corrosion. These effects are discussed in terms of the nature of the work-hardened surface layer and the chemical activity of this layer.     

Laboratory studies on the wear of grinding media

Quartzite ore was ground in a laboratory mill at different mill speeds and under dry and wet conditions using hyper steel and high chromium cast iron balls. A study of ball dynamics in the mill and scanning electron microscopy of the used ball surface threw light on ball wear characteristics and the efficiency of the grinding processes.     

The role of lubrication and corrosion in abrasion of materials in aqueous environments

A rubber wheel type test apparatus has been constructed which allows abrasion testing to be conducted in slurry or dry environments in otherwise identical conditions. Abrasion tests of a steel, a sintered tungsten carbide–cobalt hardmetal and an HVOF sprayed nickel chrome–chromium carbide cermet coating have been performed in dry and aqueous slurry conditions, the latter with both neutral and acidic carriers. It has been shown that the aqueous carrier acts as an effective lubricant and thus significantly reduces the abrasion rate over that observed in dry conditions. However, enhancement of corrosion by use of an acid slurry lead to an increase in the rate of material removal over that of the neutral aqueous conditions in all cases. Increases were small for the corrosion resistant cermet coating and moderate for the steel. Significant enhancement of wear was observed for the sintered WC–Co hardmetal where rapid removal of the cobalt binder by the acid resulted in a change in dominant mechanism of carbide removal from attritive wear to pullout.     

A study on wear mechanism and wear reduction strategies in grinding wheels used for ELID grinding

Metal-bonded superabrasive diamond grinding wheels have superior qualities such as high bond strength, high stability and high grindability. The major problems encountered are wheel loading and glazing, which impedes the effectiveness of the grinding wheel. Electrolytic in-process dressing (ELID) is an effective method to dress the grinding wheel during grinding. The wear mechanism of metal-bonded grinding wheels dressed using ELID is different form the conventional grinding methods because the bond strength of the wheel-working surface is reduced by electrolysis. The reduction of bond strength reduces the grit-depth-of-cut and hence the surface finish is improved. The oxide layer formed on the surface of the grinding wheel experiences macrofracture at the end of wheel life while machining hard and brittle workpieces. When the wheel wear is dominated by macrofracture, the wheel-working surface is free from loaded chips and worn diamond grits. When the oxide layer is removed from the wheel surface, the electrical conductivity of the grinding wheel increases, and that stimulates electrolytic dressing. The conditions applied to the pulse current influence the amount of layer oxidizing from the grinding wheel surface. Longer pulse ‘on’ time increases the wheel wear. Shorter pulse ‘on’ time can be selected for a courser grit size wheel since that type of wheel needs high grinding efficiency. Equal pulse ‘on’ and ‘off’ time is desired for finer grit size wheels to obtain stable and ultraprecision surface finish.     

Corrosive and abrasive wear in ore grinding

The relative significance of corrosive and abrasive wear in ore grinding is discussed. Laboratory marked ball wear tests were carried out with magnetic taconite and quartzite under different conditions, namely dry, wet and in the presence of an organic liquid. The effect of different modes of aeration and of pyrrhotite addition on the ball wear using mild steel, high carbon low alloy steel and austenitic stainless steel balls was evaluated. Results indicate that abrasive wear plays a significant role in ore grinding in the absence of sulfides, and rheological properties of the ore slurry influenced such wear. The effect of oxygen on corrosive wear becomes increasingly felt in the presence of a sulfide mineral such as pyrrhotite. Wear characteristics of the three types of ball materials under different grinding conditions are illustrated.     

Mechanical modelling of micro-scale abrasion in superfinish belt grinding

In synchronized transmission, the shift lever force and corresponding shiftability are the most important design considerations. The present paper introduces an engineering attempt to rigorously model a synchronizing functional surface (cone surface of idler gear) according to its finish specifications. The virtual input surface is generated by an original fractal function, which reproduces the surface “signature” due to the wheel grinding process. To model the subsequent superfinishing operation by belt finishing process, which uses a soft-coated belt as a tool, an algorithm simulating the abrasive polishing conditions is especially developed and applied to rework the initial fractal surface. The basic idea of this model is that the higher the height of a peak of the profile, the lower its probability of resistance during an abrasion cycle. The belt finishing process is hence modeled by five parameters: two parameters that characterize the initial surface (fractal dimension and range amplitude) and three parameters describing the abrasion polishing process (probability of resistance, wear volume and the number of abrasion cycles). In order to ascertain that the component will be manufactured to the required specifications, the model's parameters have to be determined. For this goal, a functional model with an optimization scheme is created. This simulation provides the morphology of the initial surface and how to cope with the superfinishing process to obtain the functionality of the surface. An elevated initial roughness is required from which slow erosion is proceeded to erode peaks and conserve some valleys of the initial profile (lubricant tanks). Finally, it is shown that automotive designers impose morphological specifications obtained by the belt grinding process to prevent scuffing of the motor parts.     

Metal transfer and wear in fine grinding

The transfer and wear characteristics of two widely used abrasive materials (A1₂O₃ and SiC) are studied when grinding two difficult materials (AISI T15 tool steel and Ti-6Al-4V titanium alloy). A newly developed accelerated wear technique (cluster overcut flygrinding) is employed together with Auger electron spectroscopy, X-ray diffraction and scanning transmission electron microscopy. Experimental results suggest that when grinding steel the wear of SiC is primarily due to oxidation, while the wear of Al₂O₃ is primarily due to metal build-up, resulting in microchipping. When a titanium alloy is being ground, both types of abrasive result in a microchipping type of wear, the rate of which decreases when the wheel speed is reduced.     

Principles for developing grinding media with increased wear resistance. Part 1. Abrasive wear resistance of iron-based alloys

Laboratory tests of iron-based alloys for abrasive wear show that the best wear resistance of the alloys with both the martensite and austenite metallic matrix is achieved in the iron-carbon system. The greater the content of alloying elements in the austenite, the more pronounced is the reduction of its wear resistance due to alloying. It is revealed that the content of the alloying elements in the wear-resistant alloys for grinding media must be as low as possible, but yet sufficient to ensure the required manufacturability of articles.     

Principles of development of grinding media with increased wear resistance. Part 2. Optimization of steel composition to suit conditions of operation of grinding media

The compositions of wear-resistant steels used as the material for grinding media are validated in order to obtain the optimal relation between the wear resistance and cost. Mathematical experiment planning reveals that low-alloyed hypereutectiod steels with the austenite-martensite structure without secondary carbides and eutectoid steels with the tempered martensite structure are the most promising for impact-abrasivecorrosive wear conditions.     

Friction coefficient and wear mode transition in micro-scale abrasion tests

The purpose of this work was to conduct ball-cratering wear tests to monitor both normal and tangential forces. Balls of 52100 steel, a specimen of H10 tool steel and an abrasive slurry prepared with silicon carbide particles and distilled water were used. Optical microscopy analysis of the worn craters revealed the presence of only grooving abrasion. However, a more detailed analysis conducted by SEM has indicated that different degrees of rolling abrasion have also occurred along the grooves. The results also showed that the normal force plays an important role in the scattering of the values of the friction coefficient.     

Friction coefficient and wear mode transition in micro-scale abrasion tests

The purpose of this work was to conduct ball-cratering wear tests to monitor both normal and tangential forces. Balls of 52100 steel, a specimen of H10 tool steel and an abrasive slurry prepared with silicon carbide particles and distilled water were used. Optical microscopy analysis of the worn craters revealed the presence of only grooving abrasion. However, a more detailed analysis conducted by SEM has indicated that different degrees of rolling abrasion have also occurred along the grooves. The results also showed that the normal force plays an important role in the scattering of the values of the friction coefficient.     

A statistical model describing wear traces in three-body abrasion

Cutting wear is a mechanism by which material is removed through three-body abrasion. In the present paper, a statistical model describing the wear traces on a worn surface is proposed for three-body abrasion, to estimate cutting wear as a proportion of the total wear of the test materials. Using this model, a statistical analysis of the traces on the worn surface was made after short-travel, three-body abrasion tests. The results showed that cutting was not a great proportion of the total wear of the test materials under the conditions of three-body abrasion.     

Some observations on profile wear in creep-feed grinding

Tests were performed to investigate the effect of various parameters on the wear of a profiled grinding wheel when creep-feed grinding a nickel-base alloy. The wear of a number of different radii, angles and profile heights was monitored. It was found that this wear was strongly influenced by the total distance travelled by an individual grit while in contact with the workpiece and by the workpiece feed rate. In addition, using a neat oil grinding fluid resulted in less wear than a water-based fluid and a 120 grit wheel wore less than a 60–80 grit wheel. A simple theoretical model was developed for predicting the effect of stock removal rate on profile wear in the creep-feed grinding of a “difficult-to-grind” material and this gave good correlation with the experimental trends.     

The role of cooling in creep feed grinding

This paper concerns the thermal aspects of creep feed grinding, as contrasted to conventional grinding. The importance of adequate cooling in creep feed grinding is well known. Without cooling, the grinding temperature in creep feed grinding would be higher than in conventional grinding. Fortunately, coolant application has been seen to be very effective in reducing the grinding temperature in creep feed grinding. In fact, while cooling is more crucial in creep feed than in conventional grinding, it is also more effective in creep feed grinding.     

Some microscopical investigations of grinding and abrasive wear*

This work forms part of a broader investigation which explores the relationship between grinding and abrasive wear. Wear experiments were performed over a wide range of loads and speeds in which solid abrasives (typical of those in grinding wheels) were rubbed against metals (usually steels). Under certain conditions the rate of wear decreased with time; at the same time the worn debris changed from metallic particles to finely divided oxides and the surface of the abrasive became glazed. Optical and scanning electron microscopy have been used to study this transition in the wear mechanism and its relationship to the structure of abrasives and the nature of abraded surfaces. The investigation illustrates the role of microscopy in the examination of a complex engineering process.     

Formation of wear debris by the abrasion of ductile metals

Decohesion of wear debris by abrasive particles was studied using polycrystalline pure metals and alloys. Wear debris were formed by steel riders with attack angles of 30°, 60° and 90° and also in the pin-on-disk test on commercial abrasive paper. Microstructural changes due to abrasion were investigated by transmission electron microscopy and X-ray diffraction examination of wear debris and worn surfaces. Simple models for the interaction between abrasive particles and material surfaces used to estimate friction and wear provided a better quantitative understanding of the influence of microstructural factors such as hardness, work hardening, crystal structure, anisotropy and phase transformation.     

The processes accompanying metal wear in polymer-containing abrasive media

The lapping process was studied. It was found that metal wear is determined by a series of factors: polymer or oligomer quantity in the heterophase system, lapping-in pressure, working time of the polymerabrasive paste or suspension and the accumulation of particles from the lapped metal.     

A study on the formation of wear debris during abrasion

A set of five material specimens have been tested on five abrasives, some of which are harder, some softer than the materials, using the dynamic abrasive wear tester. Characteristics of selected wear debris have been observed by sem and wear debris of 9Cr2Mo steel analysed by Mossbauer spectroscopy. The test results show three wear mechanisms operating during abrasion: microcutting, plougging deformation and brittle fragmentation. Different abrasives formed different constituents of wear debris due to dissimilar wear conditions. Softer abrasive tended to form more ploughing debris, although some typical microcutting chips were produced. Crushing strength of abrasive may be an important factor in addition to hardness of abrasive. The microstructure of 9Cr2Mo steel wear debris has been changed by abrasion heat; this temperature could be estimated by Mossbauer spectroscopy.     

The corrosion wear behaviour of selected stainless steels in potash brine

Tests were conducted at 25 and 85 °C to evaluate the corrosion wear resistance of selected stainless steels in potash brine using a reciprocating motion wear apparatus. Four materials were tested: Ferralium 255 (UNS S32550), AL6XN (UNS N08367), 254SMO (UNS S31254) and AISI 1018 (UNS G10180) for comparative purposes. The evaluation methods employed included weight loss analysis, optical microscopy and scanning electron microscopy (SEM). The results show that Ferralium 255 has superior corrosion wear resistance in potash brine environment compared to AISI 1018 plain-carbon steel and the other stainless steels tested. Wear surface analysis using SEM shows evidence of brittle fracture damage, which is attributed to the presence of Cl⁻.     

Automatic compensation for grinding wheel wear by pressure based in-process measurement in wet grinding

This paper deals with an application to automatic compensation of grinding wheel wear by a pressure based in-process measurement method in wet grinding. A pressure sensor is set beside a grinding wheel with a small gap. When grinding fluid is dragged into the gap by the rotation, hydrodynamic pressure, which corresponds to the gap length and the topography, can be measured. No electromagnetic properties of the workpiece and grinding wheel affect measured results. This method is applied to a CNC surface grinding machine. The pressure distribution and the relationship between the pressure and the gap length are measured. The pressure is decreased with the increase of the gap length. Its dispersion is around 1% for 0.5 μm-wear of a grinding wheel with 250 μm grit size. The dimensional error of a workpiece using the feedback of the wear is less than the feeding step, for the compensation, of 1 μm.