Manish Roy

The effect of participate reinforcement on the sliding wear behavior of aluminum matrix composites

The aim of the present investigation is to characterize the friction and wear behavior of aluminum matrix composites reinforced with particulates of SiC, TiC, TiB2, and B4C. Sliding wear tests were conducted at two loads (80 and 160 N) using a pin-on-disc apparatus and under dry conditions. The results of the investigation indicate that the coefficient of friction of the composites is about 30 pct lower than that of pure aluminum, while the wear rates of the com- posites are lower by a factor of about 3 and 100 at loads of 80 and 160 N, respectively. The type and size of the reinforcement have a negligible influence on the wear rate and the coefficient of friction of the composites. However, the volume fraction of the reinforcement has a marginal influence on the wear rate. Though the coefficients of friction and the wear rates of the com- posites were broadly similar, the Al-TiC composite alone exhibits a somewhat higher wear rate. The above results of the present investigation have been rationalized on the basis of the inverse rule of mixtures and the existing models for friction and wear.

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.

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.

Tribo-electrochemical characterization of metallic biomaterials for total joint replacement

Knee and hip joint replacement implants involve a sliding contact between the femoral component and the tibial or acetabular component immersed in body fluids, thus making the metallic parts susceptible to tribocorrosion. Micro-motions occur at points of fixation leading to debris and ion release by fretting corrosion. β-Titanium alloys are potential biomaterials for joint prostheses due to their biocompatibility and compatibility with the mechanical properties of bone. The biotribocorrosion behavior of Ti-29Nb-13Ta-4.6Zr was studied in Hanks balanced salt solution at open circuit potential and at an applied potential in the passive region. Reciprocating sliding tribocorrosion tests were carried out against technical grade ultra high molecular weight polyethylene, while fretting corrosion tests were carried out against alumina. The wear of the alloy is insignificant when sliding against polyethylene. However, depassivation does take place, but the tested alloy showed an ability to recover its passive state during sliding. The abrasivity of the alloy depends on the electrochemical conditions of the contact, while the wear of polyethylene proceeds through third body formation and material transfer. Under fretting corrosion conditions recovery of the passive state was also achieved. In a fretting contact wear of the alloy proceeds through plastic deformation of the bulk material and wear resistance depends on the electrochemical conditions.

Microstructural degradation of plain and platinum aluminide coatings on superalloy CM247 during isothermal oxidation

AbstractIsothermal oxidation at 1100°C of a high activity plain aluminide coating and a platinum aluminide coating, developed by the pack cementation technique, on cast nickel base superalloy CM247 has been carried out with the primary objective of systematically understanding the coating degradation process during oxidation. While the weight gains during oxidation for both plain aluminide and platinum aluminide coatings follow parabolic kinetics from the very beginning of oxidation exposure, the bare alloy was seen to exhibit a considerably long initial transient oxidation period (∼20 h), beyond which the parabolic law was followed. The parabolic rate constant for the platinum aluminide coating was found to be nearly two orders of magnitude lower than that for the plain aluminide coating. Alumina was identified as the only oxide phase that formed on both plain aluminide and platinum aluminide coatings during most of the oxidation exposure, although NiAl2 O4 was also found in the case of the plain alumini...

Microstructure and mechanical properties of HVOF sprayed nanocrystalline Cr3C2-25(Ni20Cr) coating

The objectives of this work are to deposit nanocrystalline Cr3C2-25(Ni20Cr) powder by thermal spraying and to compare the performance of this coating with that obtained using conventional powder. Towards that purpose, Cr3C2-25(Ni20Cr) powders with nanocrystalline grain size and with conventional grain size were deposited using OSU-SJS high-velocity oxyfuel (HVOF) system. The microstructural features, such as morphology of the coated surface, thickness of the coating, the interface of the coating with the substrate, distribution of various phases, and grain sizes etc, were characterized with the help of optical microscope, scanning electron microscope (SEM), and transmission electron microscope (TEM). The amount of oxide phases and pores were determined by means of image analyzer. The presence of various phases was identified by x-ray diffraction (XRD) technique. Hardness, elastic modulus, and indentation toughness were evaluated employing micro indentation technique. The results indicate the presence of three different zones containing only orthorhombic Cr3C2 phase, FCC NiCr phase, and mixture of Cr3C2 and NiCr phases in, both coatings. The grain sizes in the nanocrystalline coating were in the range of 80 to 100 nm. Nanocrystalline coating exhibits 20% increase in hardness, 40% decrease in surface roughness, and comparable fracture toughness and elastic modulus with respect to conventional coating.

Elevated temperature erosive wear of metallic materials

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.

Effect of particle shape on the erosion of Cu and its alloys

Abstract The main objective of the present work is to evaluate the effect of stacking fault energy (SFE) on the erosion rate of Cu and Cu-base alloys using angular particles as erodents and to compare the above behaviour with the obtained in an earlier study using spherical particles as erodents. Towards the above purpose the erosions rates of Cu, Cu-5.3 Al and Cu-20Zn were determined at two different impact angles (90° and 30°), at two different impact velocities and using angular SiC and SiO 2 particles as erodents. The results indicate that the erosion rate of Cu and its alloys decreases with increased SFE and further increases with decreasing impact angle indicative of a ductile response. This is in contrast to the erosion behaviour of Cu and its alloys, with spherical steel shots as erodents, wherein the erosion rate increased with an increase in SFE and also exhibited a maximum at normal impact angle. This contrasting erosion behaviour has been attributed to the higher strain rate and hence reduced dynamic recovery with angular particles when compared with spherical particles.

Room temperature erosion behaviour of a precipitation hardened stainless steel

Abstract The main objective of the present investigation was to compare the room temperature erosion behaviour of precipitation hardened (PH) stainless steel in the solution-treated, aged, and overaged conditions and also to evaluate the effect of erodent size and hardness on the erosion behaviour of the steel. The erosion rates of PH stainless steel in all the three heat-treated conditions were determined over a range of impact angles and velocities and with SiC and SiO2 (of two sizes) as erodent. The heat treatment of PH stainless steel had only a marginal effect on the erosion rate irrespective of impact angle and velocity even though such a heat treatment altered the mechanical properties considerably. The erosion rate always exhibited a maximum value at an impact angle of 30° irrespective of the erosion test conditions indicating a ductile erosion response. It was also observed that the erosion rate was independent of size and hardness of the erodent. The marginal effect of material strength and ductility on the erosion rates of PH stainless steel in different heat-treated conditions were rationalized qualitatively on the basis of the localization model.