Wear Mechanism of Abrasive Gas Jet Erosion on a Rock and the Effect of Abrasive Hardness on It

The existing erosion models of abrasive gas jet tend to neglect the effects of the rebounding abrasive. To address this shortcoming, abrasive wear tests were conducted on limestone by using an abrasive gas jet containing different types of particles and with different standoff distances. The results indicate that erosion pits have the shape of an inverted cone and a hemispherical bottom. An annular platform above the hemispherical bottom connects the bottom with the side of the pit. The primary cause of the peculiar pit shape is the flow field geometry of the gas jet with its entrained particles. There is an annular region between the axis and boundary of the abrasive gas jet, and it contains no abrasive. Particles swirling around the axis form a hemispherical bottom. After rebounding, the abrasive with the highest velocity enlarges the diameters of both the hemispherical bottom and erosion pit and induces the formation of an annular platform. The surface features of different areas of the erosion pit are characterized using a scanning electron microscope (SEM). It can be concluded that the failure modes for different locations are different. The failure is caused by an impact stress wave of the incident abrasive at the bottom. Plastic deformation is the primary failure mode induced by rebounding particles at the sides of the hemispherical bottom. The plastic deformation induced by the incident abrasive and fatigue failure induced by the rebounding abrasive are the primary failure modes on the annular platform. Fatigue failure induced by rebounding particles is the primary mode at the sides of the erosion pits. The rock failure mechanism that occurs for particles with different hardness is the same, but the rock damaged by the hard abrasive has a rougher surface.

The Abrasive Wear Resistance of Chromium Cast Iron

The resistance of cast iron to abrasive wear depends on the metal abrasive hardness ratio. For example, hardness of the structural constituents of the cast iron metal matrix is lower than the hardness of ordinary silica sand. Also cementite, the basic component of unalloyed white cast iron, has hardness lower than the hardness of silica. Some resistance to the abrasive effect of the aforementioned silica sand can provide the chromium white cast iron containing in its structure a large amount of (Cr, Fe)7C3 carbides characterised by hardness higher than the hardness of the silica sand in question. In the present study, it has been anticipated that the white cast iron structure will be changed by changing the type of metal matrix and the type of carbides present in this matrix, which will greatly expand the application area of castings under the harsh operating conditions of abrasive wear. Moreover, the study compares the results of abrasive wear resistance tests performed on the examined types of cast iron. Tests of abrasive wear resistance were carried out on a Miller machine. Samples of standard dimensions were exposed to abrasion in a double to-and-fro movement, sliding against the bottom of a trough filled with an aqueous abrasive mixture containing SiC + distilled water. The obtained results of changes in the sample weight were approximated with a power curve and shown further in the study.

Analysis of the Structure and Abrasive Wear Resistance of White Cast Iron with Precipitates of Carbides

The resistance of castings to abrasive wear depends on the cast iron abrasive hardness ratio. It has been anticipated that the white cast iron structure will be changed by changing the type of metal matrix and the type of carbides present in this matrix, which will greatly expand the application area of castings under the harsh operating conditions of abrasive wear. Detailed metallographic analysis was carried out to see the structure obtained in selected types of white cast iron, i.e. with additions of chromium and vanadium. The study compares the results of abrasive wear resistance tests performed on the examined types of cast iron.

Theoretical and Experimental Analysis of the Influence of Abrasives on Nozzle in Pre-Mixed Abrasive Water Jet

This paper introduces the influence of the shape, grain size, density and hardness of abrasives particles on nozzle wear. Different parameters of abrasive hardness are investigated through theoretic and experimental analysis. The results show that the ratio of abrasive hardness to nozzle material hardness governs the wear rate Ca.

Effect of Abrasive on the Machining Performance the EMR-Effect-Based Tiny-Grinding Wheel

Based on the electro-magneto-rheological (EMR) effect, the Fe3O4-based EMR fluid dispersed with micron-sized finishing abrasives is used as a polishing fluid to form a dynamical tiny-grinding wheel under an electro-magnetically coupled field. Using this EMR-effect-based tiny-grinding wheel, experiments were conducted to investigate the effect of the grain size, content and material of abrasive on material removal effect of normal glass. Results indicate that the abrasive can change the chain-like structure of the EMR-effect-based tiny-grinding wheel and influence the material removal ability of the tiny-grinding wheel remarkably. The material removal amount increases with the increase of the content of diamond abrasive in the EMR fluid, and grows slowly when the proportion of diamond abrasive exceeds to 6%. While the grain size of abrasive increases, the material removal amount increases at the beginning and decreases afterwards. The effect of abrasive on material removal depends on the hardness of abrasive, the greater the abrasive hardness, the higher the material removal efficiency. The machined area has a close relationship with both the density and grain size of abrasive.

An Overview of the Hardness Differential Required for Abrasion

This paper presents an overview of the hardness differential required for abrasion. Empirically, the abrasive must be at least 1.2 times harder than the worn surface if it is to produce a scratch. This value has been determined theoretically using slip-line field modeling, which assumes rigid-plastic mechanical behavior, an assumption that is inadequate for most abrasive particles. Two approaches using elastic-plastic models and three tribological pairs with similar ratios of abrasive hardness to worn material hardness were tested to gain an understanding of the hardness differential required for abrasion. The analysis showed that the ratios of the property of the abrasive to the property of the worn surface did not change with the model used when the mechanical behavior of the materials was similar. However, when the behavior of the materials was very dissimilar—as is often the case in abrasive processes—the ratios varied greatly depending on the model used, showing that there is a need for models to describe the hardness differential required for abrasion.

Effect of abrasive material properties on polishing rate selectivity of nitrogen-doped Ge2Sb2Te5to SiO2film in chemical mechanical polishing

We investigated the polishing rate and selectivity of nitrogen-doped Ge2Sb2Te5(NGST) to SiO2film for different abrasive materials (colloidal silica, fumed silica, and ceria abrasives). They both were strongly dependant on abrasive material properties. The polishing rate of nitrogen-doped NGST decreased in the order ceria, fumed silica, and colloidal silica abrasives, which was determined by abrasive material properties, such as abrasive hardness, crystal structure, and primary and secondary abrasive sizes. In addition, the polishing rate slope of NGST film was not significantly different for different abrasive materials, indicating that the polishing of NGST film is mechanical dominant polishing. In contrast, the polishing rate slope of SiO2film decreased in the order ceria, fumed silica, and colloidal silica abrasives, indicating that the polishing of SiO2film is chemical dominant polishing. Furthermore, the difference in polishing rate slopes between NGST and SiO2film gave a polishing rate selectivity of NGST to SiO2film higher than 100:1 with colloidal silica abrasive.

A Review of the Abrasive Wear of Metals

A survey is presented of the experimental work which has been carried out on the abrasive wear of metals. The effect of variables such as surface hardness, abrasive hardness, abrasive particle size, and velocity are discussed for several types of abrasive wear. The similarities between different types of wear are described with the viewpoint of using one type of wear test to rank materials for another application.