Copper Fly Ash Tungsten Composites Properties

By Nydia Ortega

The copper fly ash tungsten composites has gained attention in recent years due to their unique properties and potential applications. This paper, authored by Nydia Ortega, explores the mechanical and corrosion behavior of copper fly ash tungsten hybrid composites, with a focus on their properties. The composites were prepared using powder metallurgy techniques and sintering processes. The resulting microstructure, grain size, porosity, density, and hardness were analyzed. The mechanical properties, including tensile strength, compressive strength, flexural strength, fatigue strength, and creep behavior, were also examined. In addition, the wear resistance and wear behavior of the composites were evaluated, including tribology, friction, sliding wear, abrasive wear, erosive wear, and the underlying wear mechanisms. The corrosion resistance and corrosion mechanisms of the composites were also studied, including electrochemical behavior. Thermal properties such as thermal conductivity, thermal expansion coefficient, specific heat, melting temperature, and solidification behavior were also investigated. The composites' casting, machining, surface roughness, and surface morphology were analyzed using various techniques such as scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Overall, this study provides valuable insights into the properties and potential applications of copper fly ash tungsten composites. The findings can be used to optimize the fabrication process, enhance the mechanical and corrosion properties, and expand the range of applications for these unique materials.

• Language: English
• Publisher: Nydia Ortega
• Release date: Jul 1, 2024
• ISBN: 9798227565006

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ABSTRACT

Copper is one of the important nonferrous metal that has been used widely in various industries such as heat exchangers, microelectronics, water distribution networks, materials for nozzles of gas turbines, contact breakers and neutron target materials, liners of combustion chamber walls and also employed highly for sculptures, monuments, outdoor decorative building materials etc. The above application requires properties like good wear resistance, corrosion resistance, good strength, hardness, porosity, good thermal conductivity etc. . Pure copper failed because of its poor wear resistance, soft and ductility. Hence copper based composite materials are evolved with different fabrication and processing techniques. Each method of fabrication or processing or reinforcement in copper has certain advantages and disadvantages. Another important aspect of which industries look for the above said application is the amount of reduction in weight and its cost with an appropriate strength, wear, hardness, and its related properties etc. The reduction in cost and weight of the material also depends on the density of the reinforcing material and its cost. One such reinforcement material that has a low density and cheaper is Fly ash (FA) which is a residue obtained by burning coal. Many developing countries are utilizing coal as the main source of energy for producing electricity. In India, the Gazette, Ministry of Environment and Climate Change (MoECC), India. has published a notification on 27th January 2016 that all the coal based power plants have to utilize the FA by 100 % which is produced by them. Hence many industries started to utilize the FA in various sectors.

Hence, in this research, an attempt has been made to utilize the FA by reinforcing FA in Cu by fabricating two sets of composite materials. The first set of the composite was fabricated by the addition of single low density reinforcement to form Cu-FA composite material with sample proportions of

3, 6 and 9 wt.% of FA in the Cu matrix. FA was collected from the Electrostatic precipitator of Tuticorin thermal power station, Tuticorin, Tamil Nadu, India. The second set of the composite was fabricated by the addition of two reinforcements. The first reinforcement material FA is kept 6 wt.% as constant in Cu and the second reinforcement used was tungsten (W). W was added in 3, 6 and 9 wt.% to form Cu-6FA-3W, Cu-6FA-6W and Cu-6FA-9W hybrid composite material. The most popular and conventional powder metallurgy (P/M) method was used to fabricate the preforms and the effect of reinforcements was investigated by varying the wt.% distribution.

The prepared samples were subjected to various characterization such as structural, mechanical, wear and corrosion resistance properties. Scanning Electron Microscopy (SEM) analysis was used to study the morphology of the composite materials. The X-ray diffraction analysis was used to characterize the elemental composition of composite powder. Energy-dispersive spectroscopy (EDS) with mapping was used to find the homogeneous distribution of reinforcements in the Cu matrix. Theoretical and sintered density was measured by the rule of mixture and Archimedean principle. Mechanical characterization of Cu-FA composite and Cu-FA-W hybrid composite material was studied using vickers hardness and compression test.

In this study, it was observed that the density of the composite decreases with an increase in wt.% addition of FA. The lowest density of 7.503g/cm3 was recorded for Cu-9FA which is 6.78 times lower than the Cu. When W and FA were added in the Cu matrix to form Cu-FA-W hybrid composites, the density initially reduced by 2.19 % with respect to Cu for Cu- 6FA-3W. Further increase in addition of wt.% W increases the density of the hybrid composites due to the addition of high density W reinforcement.

Microhardness of composites was measured using Vickers hardness testing machine. It was observed that the hardness of the fabricated composites increases with an increase in % reinforcement of both FA as well as W. The improvement in hardness of Cu-FA was observed to be low when compared to Cu-FA-W hybrid composite material due to dual reinforcement of ceramic and metallic reinforcement and presence of W.

Compression test was conducted on the fabricated composites using a universal testing machine. The results of the compression test revealed that the compressive strength of Cu-FA composites shows a decrease in trend whereas, for Cu-FA-W hybrid composites, it shows an increase in trend. Boundary slip was the mechanism that has been happened in Cu-FA composites. The addition of high density W transfers the applied load and could resist the dislocation thereby increasing the compressive strength of the composite material.

The tribological properties of Cu-FA and Cu-FA-W specimens were investigated using Pin-on disc tribo testing machine against EN81 steel contour disc for the sliding velocity of 1 m/s, 2 m/s and 3 m/s, sliding load of 10 N, 15 N and 20 N against the sliding distance of 2000 m. The effect of sliding velocity at different loads on specific wear rate (SWR) and the coefficient of friction (CoF) was discussed. In the case of single reinforcement, Cu-9FA has the lowest SWR compared to other Cu-3FA and Cu-6FA . In the case of dual reinforcements, Cu-6FA-6W records the highest wear resistance which was 10-15% superior when compared to Cu-6FA-3W and Cu-6FA-9W. Overall from 6 different compositions, Cu-6FA-6W has the highest wear resistance which was 10% superior to Cu-9FA composites.

The corrosion behavior of the fabricated composites was studied using an electrochemical workstation in acidic (1N HCl) and seawater. Cu- 9FA and Cu-6FA-9W exhibits good corrosion resistance than pure Cu in both the media. Their increase in charge transfer resistance of Electrochemical

Impedance Spectroscopy (EIS) test authenticates and confirms their corrosion resistivity.

LIST OF TABLES

TABLE NO. TITLE PAGE NO.

Comparison of different processing Techniques 16

ASM international standard of copper 33

2.1 Various chemical composition of Indian FA 46

Characteristics of Electrolytic Cu powder of Grade

EC1 and W powder 66

Fabricated composites with compositions 67

Density and Porosity of Pure Cu & Cu - FA

composite 81

Ecorr, Icorr and Polarization resistance of Cu-FA

composite material in 1N HCl and in Sea water 95

Charge transfer resistance data by EIS fitting 97

Sintered Density, Porosity and relative density of

fabricated hybrid composites 105

Ecorr , Icorr and Polarization resistance of Cu-FA

composite material in 1N HCl and in Sea water 119

Charge transfer resistance data by EIS fitting 121

SWR and CoF of Cu-FA and Cu-FA-W composites

at various load and sliding velocity 130

Ecorr , Icorr and Polarization resistance of Cu-FA

and Cu-FA-W hybrid composite material in 1N HCl

and in Sea water 140

Green Compacts after compaction process 68

Pin-on Disc Experimental setup 71

Photograph of the electrochemical workstation 72

Outline of the experimental investigation of

Cu-FA composites 75

(a) Particle Size distribution of Cu and (b) Particle

size distribution of FA 76

(a) SEM of FA particles (b) SEM micrograph of

Cu (c) SEM micrograph of Cu-3FA 77

EDS dot mapping image of Cu-9FA 79

XRD of the Cu - FA composite 80

Vickers Hardness of Cu-FA composite 82

(a-b) FA particles in Cu Matrix (c) Effect of

compressive strength of Cu-FA composite 84

Schematic diagram of the model 85

(a) Schematic diagram shows interstitial type

reinforcement (filling the voids) (b) - surplus addition

of reinforcement in matrix 86

(a - c) Effect of Sliding Velocities on SWR of

Cu-FA composites at different loading conditions 87

Worn surface of Cu-3FA at 10 N load and 1 mIs

sliding velocity 90

Worn surface analysis of (a) Cu-3FA at 3mIs and load 20 N, (b) Cu-6FA at 3 mIs and load 20 N and

(c) Cu-9FA at 1 mIs and load 10 N 91

(a - c) Effect of Sliding Velocities on CoF of

Cu-FA composites at different loading conditions 93

Potentiodynamic polarization curve of Cu-FA

(a)  Cu-FA in 1N HCl and (b) Cu-FA in sea water 96

EIS graph of Cu-FA composites in 1N HCl medium 98

EDS dot image Mapping of Cu-6FA-3W 102

EDS dot image Mapping of Cu-6FA-6W 103

EDS dot image and Mapping of Cu-6FA-9W 104

Vickers hardness of Cu-FA-W hybrid Composites 107

Compressive strength of Cu-FA-W hybrid

composites 107

Schematic representation of distribution of

matrix and reinforcements in compression 109

(a - c) Effect of Sliding Velocities on SWR of Cu-FA-W hybrid composites at different

loading conditions 110

Worn surface analysis of Pure Cu 112

Worn surface analysis of Cu-6FA-3W 113

Worn surface analysis of Cu-6FA-6W 114