Characterization of Cold Sprayed Copper Coatings on Al Alloy Substrate

Characterization of Cold Sprayed Copper Coatings on Al Alloy Substrate

Tarun Goyal (SUS College of Engineering and Technology, Mohali, India), T. S. Sidhu (Shaheed Bhagat Singh State Technical Campus, Ferozepur, India) and R. S. Walia (Delhi Technological University, Delhi, India)
DOI: 10.4018/IJSEIMS.2015070103
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Abstract

This study reveals the successful low pressure cold spray deposition of near-uniform, defect free and dense copper coatings approximately 700-1900 µm thick, on Al alloy for electro-technical applications. The micro structural characteristics of the deposits have been studied using the combined techniques of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) and electron-probe micro analysis (EPMA). The coatings exhibited characteristic splat-like, layered morphologies due to the deposition of solid powder particles which appeared to have been plastically deformed on impact to the substrate. The developed coatings have a dense (in the range of 3090-5015 kg/m3)and nearly uniform microstructure, with almost uniform hardness values in the range of 120 -140 Hv, and electrical conductivity in the range of 23-30 MS/m. EDAX, XRD and EPMA results revealed that the main constituent in the coating is Cu.
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1. Introduction

Surface treatment procedures are used to modify the surface properties of various materials without altering their bulk characteristics. These techniques are used within industrial environments to improve resistance to corrosion, wear, fatigue, and heat. A comparison of competitive spraying technologies clearly shows that cold gas dynamic spraying has been established as a viable coating technology in the thermal spray processes family. The dense and oxide-free coatings that may be produced through Gas Dynamic Spraying (GDS) have brought about a multitude of new applications which, up to now, have not been feasible using traditional processes (Jeandin et al., 2014). The practical solutions may be readily observed within automotive and electronics manufacturing industries. However, despite this great progress, the full potential of high-pressure and low-pressure GDS has not yet been fully realized (Maev & Leshchynsky, 2008 and Bala et al., 2014). Cold spray coatings may be classified as high-pressure cold spray and low pressure cold spray on the basis of the stagnation pressure of the working gas. Table 1 makes a comparison of two versions of the cold spray process according to operating parameters.

Table 1.
Operating parameters (Maev & Leshchynsky, 2008)
Process CharacteristicHigh-Pressure SystemLow-Pressure System
Working gasN2, He, airN2, air
Gas pressure, MPa2.5 – 4.50.5 – 1.0
Gas preheat, 0C20 - 80020 - 550
Gas flow rate, m3/hr50 - 15015 - 30
Maximum gas Mach No.1 - 31 - 3
Powder flow rate, g/s0.1 – 1.00.1 – 1.0
Particle size, µm5 - 10010 - 80

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