G. Sundararajan

The solid particle erosion of polymer matrix composites

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.

Solid particle erosion behaviour of metallic materials at room and elevated temperatures

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.

A comprehensive model for the solid particle erosion of ductile materials

An exhaustive database presently exists on the influence of various test and material-related parameters on the solid particle erosion behaviour of metallic materials. However, the understanding of the micromechanisms responsible for material removal during erosion is far from complete. This is especially true for erosion at oblique impact angles, where the role of the near-surface shear layer formed by the frictional force between the impacting particle and the eroding material is still unclear. The objective of the present paper is to develop a comprehensive theoretical model for erosion, valid for all impact angles, combining the concept of localization of plastic deformation leading to lip formation and the generalized energy absorption relations valid for all impact angles and all shapes of eroding particles.

Erosion efficiency-a new parameter to characterize the dominant erosion micromechanism

A new parameter called erosion efficiency, capable of identifying the dominant micromechanism leading to solid particle erosion, has been introduced in this paper. The objective of this paper is to demonstrate the usefulness of this parameter by considering the large body of data in the literature pertaining to the solid particle erosion of metallic materials, ceramics, cermets and coatings under normal impact conditions.

The depth of plastic deformation beneath eroded surfaces: The influence of impact angle and velocity, particle shape and material properties☆

Abstract The solid particle erosion behaviour of a variety of metals and alloys has been characterized over the past years. However, very little attention has been paid to the nature and size of the plastic zone that exists just beneath the eroded surface. This is indeed surprising since the size of the plastic zone is the primary parameter which determines the magnitude of the energy dissipated via plastic deformation. Thus, if the erosion rate is deformation controlled (i.e. the fracture event is easy and not rate controlling), a definite correlation should exist between the size of the plastic zone and the erosion rate. In fact the localization model for erosion, proposed earlier by the present author, predicts the erosion rate to be proportional to L3 where L is the plastic zone size. The main objective of this paper is to investigate the influence of test and material variables on the extent of the plastic zone that exists beneath the eroded surfaces. Towards this purpose the experimental data on the plastic zone size beneath eroded surfaces in a variety of metallic materials such as 304, 316 and 410 stainless steels and copper and its alloys eroded over a range of velocities and impact angles are presented. The experimental data illustrating the influence of particle shape (angular vs. spherical) and the erosion test temperature on the plastic zone size are also provided. All of the above experimental data regarding plastic zone size are rationalized on the basis of a theoretical model. Finally, the correlation that exists between the plastic zone size and the erosion rate is also emphasized.

The nature of the elastic rebound of a hard ball impacting on ductile, metallic target materials

Abstract The objective of the present investigation is to characterize the nature of the elastic rebound of a tungsten carbide ball when it is impacted against metallic target materials having a wide range with respect to hardness and elastic modulus. Ten target test materials were used and each of them was impacted by the WC ball at incident velocities of 5.5 and 7.5 m s −1 . The nature of the elastic rebound was characterized in terms of the coefficient of restitution (e) and also by the nature of and the means by which the crater formed by impact elastically recovered its shape during the rebound phase. The experimentally observed variation of e and the extent of crater recovery as a function of the test material hardness and elastic modulus and the impact velocity could be adequately explained on the basis of simple theoretical models.

An analysis of the erosion-oxidation interaction mechanisms

Materials exposed to a jet of erosive hard particles travelling at high velocities and to elevated temperatures beyond one-third of their melting point, undergo erosion as well as oxidation. Thus, it is necessary to understand the nature of the interaction between erosion and oxidation. Over the last few years, experimental data on elevated temperature erosion in an oxidizing atmosphere, particularly for steels, have become available. However, a comprehensive theoretical analysis of the erosion-oxidation (E-O) interaction is yet to be carried out. In the present paper a theoretical framework for interpreting the nature of the E-O interaction is presented. The possible erosion mechanisms involving E-O interactions are considered and their relative dominance as affected by test variables such as particle size and shape, oxidation rate, particle flux rate etc., are brought out in the form of E-O maps. A new model for the oxidation controlled erosion mechanism is also presented. Finally, a comparison is made between the predictions of the model and the experimental data available in the literature.

The solid particle erosion of metallic materials: The rationalization of the influence of material variables

Solid particle erosion, an important material degradation mechanism encountered in a number of technological and engineering systems, has been investigated intensively over the last few decades. The influence of erodent particle and particle flow related variables on the erosion behaviour is reasonably well understood. On the other hand, in spite of the availability of a large database, the effect of the properties of the eroding material on its erosion behaviour is yet to be fully clarified. Such a poor level of understanding can be primarily traced to the fact that erosion involves the deformation of the material under high strain rate, adiabatic and constrained conditions and to the fact that the properties of the material are not known under such unique deformation conditions. In this paper, the influence of the various conventional strengthening mechanisms on erosion resistance of metallic materials is first discussed. Next, the unique aspects of material deformation during erosion are highlighted and the plastic flow behaviour of metallic materials under such conditions is explored. Finally, an erosion model, incorporating the ideas brought out in the earlier sections, is presented and utilized to explain much of the available experimental data.

Room temperature erosion behaviour of 304, 316 and 410 stainless steels

Abstract The main purpose of this investigation is to compare the room temperature erosion behaviour of three stainless steels, namely 304, 316 and 410 SS. Towards this purpose, the erosion rates of all three stainless steels have been determined at three impact angles (30°, 60° and 90°) and at two impact velocities (98 and 129 m s−1) for each angle. The results indicate that while the erosion rates of 304 and 316 SS are comparable, that of 410 SS is lower by 15%–20%. The improved erosion resistance of 410 SS, in spite of its lower ductility and strain-hardening capacity as compared with 304 and 316 SS, appears to be related to the fact that the depth to which plastic deformation extends beneath the eroded surface (L) is significantly lower in 410 SS and also to the presence of a “soft zone” beneath the eroded surface.

Erosion behaviour of ductile materials with a spherical non-friable erodent

Abstract Erosion experiments were carried out on two ductile materials, copper and Cu-6%Al alloy, with an aim to study the dependence of the erosion rate on the impact angle with spherical non-friable steel shot as the erodent. The experiments were carried out at impact angles of 30°, 60° and 90° at an impact velocity of 40 m s −1 . The results indicate that the erosion rate is greatest at normal impact for the spherical erodent, in contrast with the general observation that the maximum erosion rate in ductile materials occurs at oblique impact. Scanning electron microscopy examination revealed that lip formation and lip fracture are the operating mechanisms of material removal at all impact angles studied. The experimental findings are rationalized using the localization model.