An analysis of the transition from metal erosion to oxide erosion
TL;DR: In this paper, the transition from metal erosion to oxide erosion is governed by the depth to which deformation extends beneath the oxide scale as compared to the thickness of the scale, and the results clearly establish that there is a slow transition from the metal degradation to oxide degradation as the ratio of the thickness to the depth of deformation changes from 0.5 to 3.
Abstract: The solid particle erosion of metals and alloys at elevated temperature encounters different mechanisms of interaction between erosion and oxidation, depending on the nature of the oxide scale. Two important mechanisms are metal erosion and oxide erosion. It has been postulated that the transition from metal erosion to oxide erosion is governed by the depth to which deformation extends beneath the oxide scale as compared to the thickness of the scale. In order to validate this postulate, erosion rates of NiO scale having two different thicknesses (100 μm and 20 μm) were determined as a function of impact velocity, impact angle and erodent size, and compared with that of the substrates obtained by machining the oxide scale. The results clearly establish that there is a slow transition from the metal erosion to oxide erosion as the ratio of the thickness of the oxide scale to the depth of deformation changes from 0.5 to 3.
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TL;DR: This work tries to combine and integrate existing approaches into a general simple scheme unifying known wear types into a consistent system and can be used in teaching to introduce students to such complex phenomena as wear and also in engineering practice to guide wear mitigation initiatives.
Abstract: Since the beginning of the systematic study of wear, many classification schemes have been devised. However, though covering the whole field in sum, they stay only loosely connected to each other and do not build a complete general picture. To this end, here we try to combine and integrate existing approaches into a general simple scheme unifying known wear types into a consistent system. The suggested scheme is based on three classifying criterions answering the questions “why”, “how” and “where” and defining a 3-D space filled with the known wear types. The system can be used in teaching to introduce students to such complex phenomena as wear and also in engineering practice to guide wear mitigation initiatives.
45 citations
Cites background from "An analysis of the transition from ..."
...For example, it was demonstrated that, on one hand, the oxidation rates under erosion conditions are dramatically higher than static oxidation rates [38], while, on the other hand, the erosion rate is higher under conditions of larger thickness of the oxide scale [39]....
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TL;DR: In this article, a review of the state-of-the-art understanding of the elevated temperature erosion behavior of metals and alloys is presented. But the main objective of this paper is to critically review the present state of understanding of metal erosion behavior.
Abstract: Solid particle erosion of metals and alloys at elevated temperature is governed by the nature of the interaction between erosion and oxidation, which, in turn, is determined by the thickness, pliability, morphology, adhesion characteristics and toughness of the oxide scale. The main objective of this paper is to critically review the present state of understanding of the elevated temperature erosion behaviour of metals and alloys. First of all, the erosion testing at elevated temperature is reviewed. This is followed by discussion of the essential features of elevated temperature erosion with special emphasis on microscopic observation, giving details of the erosion–oxidation (E–O) interaction mechanisms. The E–O interaction has been elaborated in the subsequent section. The E–O interaction includes E–O maps, analysis of transition criteria from one erosion mechanism to another mechanism and quantification of enhanced oxidation kinetics during erosion. Finally, the relevant areas for future studies are indicated.
35 citations
TL;DR: In this article, the authors delineate the prevalent erosion mechanisms in nickel and a nickel-20 chromium alloy over a large range of temperatures, impact velocities, impact angles, and particle feed rates.
Abstract: The solid-particle erosion of metals and alloys at elevated temperatures is characterized by different mechanisms of material removal, depending on the temperature of exposure, impact velocity, impact angle, and flux rate of the eroding particles. The objective of this article is to delineate the prevalent erosion mechanisms in nickel and a nickel-20 chromium alloy over a large range of temperatures, impact velocities, impact angles, and particle feed rates. For this purpose, a specialized elevated-temperature erosion rig has been utilized. Nickel and a Ni-20Cr alloy have been chosen as the test materials, in view of their substantially different oxidation behaviors. Results from the present study indicate that while the erosion rate generally increases with increasing temperature, an increased particle feed rate causes a reduction in the erosion rate, especially at higher temperatures beyond 650 K. On the basis of a detailed examination of the morphology of the eroded surfaces and the subsurface features beneath the eroded surfaces, four different material removal mechanisms have been identified in the nickel, while only three material removal mechanisms were operative in the Ni-20Cr alloy. Utilizing the aforementioned information, erosion-oxidation (E-O) interaction mechanism maps (herein, termed E-O maps) delineating the regions of dominance of the various erosion mechanisms in an impact velocity-test temperature space have been constructed for Ni and a Ni-20Cr alloy. Finally, the differences in erosion behavior between the Ni and Ni-20Cr alloy have been identified and rationalized.
30 citations
Dissertation•
01 Jan 2004
TL;DR: In this article, the authors investigated the micro-structural analysis of thermal spray coatings under high temperature, high erodent velocity, turbine conditions, and simulated turbine conditions.
Abstract: This thesis investigates the mechanisms of erosion-corrosion of Cr3C2-NiCr thermal spray coatings under high temperature, high erodent velocity, turbine conditions. Erosion-corrosion is a generalised wear phenomenon where the combined effect of each degradation mechanism generates more extensive mass loss than the sum of each mechanism acting independently. Previous research has highlighted several theoretical mechanisms under this generalized process, ranging from the erosion induced breakdown of oxide scales in corrosive environments, through to the development of oxide layers in highly erosive environments. Prior to this current work experimental simulation of these mechanisms has focused on bulk alloy materials with well characterised oxidation responses, under conditions of low temperature, low erodent impact velocity and high erodent flux, conditions which are readily generated within laboratory scale rigs and which tend towards the low impact energy conditions encountered within fluidised bed combustors. Few works have addressed erosion-corrosion under simulated turbine conditions of high temperature, high erodent impact velocity and low erodent flux. While comparative trials have been run under such conditions on a purely mass loss basis, little has been presented regarding the microstructural analysis of such degradation, particularly for materials that rely on the industrially relevant, slow growing oxide scales Cr2O3 and Al2O3. Thermally sprayed Cr3C2-NiCr coatings are routinely applied to combat wear at high temperature due to the high wear resistance imparted by the hard carbide particles and the high temperature oxidation resistant nature of the Cr2O3 oxide formed over both phases. However, most published work characterising the erosion-corrosion response of these coatings has been conducted on a comparative basis by contrasting coatings of various composition ratios, deposited by various techniques, with the response of well characterised bulk materials. Little has been presented on the microstructural mechanism of erosioncorrosion of Cr3C2-NiCr coatings, a point highlighted by the limited understanding of the oxidation mechanism of the Cr3C2 phase, the oxidation mechanisms of the combined composite Cr3C2-NiCr and the influence of the coating splat structure on the oxidation response. While the erosion response of thermal spray coatings and bulk cermets is more widely understood, most works have been conducted under milder conditions than used in the current work. In addition previous works have been conducted primarily on assprayed coatings with few works taking into account the effect of heat treatment induced changes in the coating composition and microstructure that occur with extended in-service exposure at elevated temperature. In addressing the short comings in the current state of knowledge, the aim of this work was to characterise the mechanism of erosion-corrosion of high velocity sprayed Cr3C2-NiCr thermal spray coatings under turbine conditions, incorporating the effect of variation in…
27 citations
TL;DR: In this paper, the hot and cold erosive wear mechanisms of HVOF and plasma-sprayed NiCr-based coatings are evaluated, with possible variations in temperature and attack angle.
Abstract: In this work, the hot and cold erosive wear mechanisms of HVOF and plasma-sprayed NiCr-based coatings are evaluated. Erosion tests were carried out in specially developed equipment, with possible variations in temperature and attack angle. The effects of erodent incrustation (SEM/EDS mapping) and oxidation of metallic coating (mass weight) were considered. The results were associated with the microstructural characteristics of the coatings (porosity, size of lamellae) and with the mechanical properties, such as microhardness and elasticity modulus. The obtained results showed that NiCr coatings are ductile, a property similar to monolithic metallic materials. The porosity influenced both the amount of incrusted alumina particles and oxidation. The increase in temperature caused higher oxidation and erodent incrustation.
25 citations
References
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TL;DR: In this article, a method for determining the velocity of solid particles in a gas-particulate stream applied to erosion testing of materials is described, where a simple mechanical configuration allows the measurement to be made under a wide range of equipment conditions.
Abstract: A method is described for determining the velocity of solid particles in a gas-particulate stream applied to erosion testing of materials. A simple mechanical configuration allows the measurement to be made under a wide range of equipment conditions. The time-of-flight of the particles is determined over a controlled path length between two rotating disks. Examples of measurements on several test apparatus are presented. The importance of nozzle design is discussed. A comparison between particle and gas stream velocity is presented.
448 citations
TL;DR: In this article, the salient features characteristic of room temperature and elevated temperature erosion of metallic materials are described and a review of some of the recent results, which in their opinion, have enhanced our current understanding in the area of solid particle erosion of metal materials.
Abstract: The behaviour of metallic materials subjected to solid particle erosion has been studied extensively over the last few decades. It is not the purpose of this paper to provide a comprehensive review of the above body of work especially since many such reviews already exist. Rather, the aim of this paper is to describe briefly the salient features characteristic of room temperature and elevated temperature erosion of metallic materials and follow it up with a review of some of the recent results, which in our opinion, have enhanced our current understanding in the area of solid particle erosion of metallic materials. As a natural consequence, the paper concludes with a critical review of the areas which require further study.
193 citations
TL;DR: In this paper, the solid particle erosion behavior of four different types of polymer matrix composites reinforced with glass fibres has been characterized and compared with the available data in the literature on similar materials.
Abstract: The solid particle erosion behaviour of four different types of polymer matrix composites reinforced with glass fibres have been characterized. The erosion rates of these composites have been evaluated at two impact angles (90° and 30°) and two impact velocities (38 and 45 m s −1 ). The erosion response, erosion efficiency and the erosion micromechanisms of these composites are presented and discussed in detail and also compared with the available data in the literature on similar materials.
161 citations
TL;DR: In this article, the authors describe a dynamic indentation (DI) technique suitable for the determination of the high strain rate flow behavior of ductile metals and alloys and illustrate its use by characterizing the high-strain rate flow behaviour of iron and OFHC copper.
Abstract: The objective of the paper is to describe a dynamic indentation (DI) technique suitable for the determination of the high strain rate flow behaviour of ductile metals and alloys and illustrate its use by characterizing the high strain rate flow behaviour of iron and OFHC copper. The DI technique is first described in detail and the dynamic hardness-strain data of iron and copper obtained using the technique is presented. It is also demonstrated that it is a suitable technique for characterizing the high strain rate flow behaviour as long as certain validity conditions are met. It is shown that these validity conditions are fully met in the case of copper and at low strain levels in iron. The reliability of the DI technique is finally demonstrated by comparing the present data with the literature data on similar materials and finally a critique of the DI technique is provided.
84 citations
TL;DR: In this paper, the results of exposure to a controlled high-temperature erosive gas stream of a series of alloys, which were selected to represent the range of microstructures and mechanical properties available in commercial hightemperature alloys.
Abstract: The results are presented of exposure to a controlled high-temperature erosive gas stream of a series of alloys, which were selected to represent the range of microstructures and mechanical properties available in commercial high-temperature alloys. Analysis of the kinetic and morphological data suggested that the high-temperature oxidation behavior of a given alloy plays a very important role in determining its erosion-corrosion behavior under the conditions studied. In terms of relative behavior, alloys which are weak but ductile at temperature, and which form tenacious oxide scales, exhibited the highest resistance to high-temperature erosion-corrosion. Simple models were developed to describe the expected interaction between high-temperature oxidation and erosion.
58 citations