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RESEARCH PAPERS

Characterization and Erosion Behavior of Plasma Sprayed NiCrAlY and Ni-20Cr Coatings on an Fe-based Superalloy

[+] Author and Article Information
S. B. Mishra1

Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee-247 667, Indiasurya_iitr@yahoo.co.in

K. Chandra, S. Prakash

Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee-247 667, India

1

Corresponding author.

J. Tribol 128(3), 469-475 (Mar 03, 2006) (7 pages) doi:10.1115/1.2197843 History: Received October 21, 2005; Revised March 03, 2006

Degradation of materials due to solid particle erosion is encountered in a variety of engineering industries, either at room temperature or elevated temperatures. Nickel-based coatings are commonly used in applications where wear resistance, combined with oxidation or hot corrosion resistance, is required. In the present work, NiCrAlY and Ni-20Cr metallic coatings were deposited on an iron-based superalloy by a shrouded plasma spray process. The coatings were characterized by scanning electron microscopy, optical microscopy, microhardness testing, and x-ray diffractometry. Erosion studies were conducted using an air-jet erosion test rig at a velocity of 40ms1 and impingement angles of 30 and 90deg. Scanning electron microscopy was used to analyze the eroded surfaces. 3D surface roughness profiles of the eroded samples were taken using a Veeco Optical Profilometer. NiCrAlY coatings had slightly lower average porosity and lower microhardness as compared to Ni-20Cr coatings. The observed erosion rate of the NiCrAlY coatings, however was lower than that of the Ni-20Cr coatings at both 30 and 90deg impingement angles. Ni-20Cr coating had shown higher erosion rate at 90deg impingement angle than that at 30deg, whereas the effect of impingement angle on the erosion rate is negligible for plasma sprayed NiCrAlY coating. The higher bond strength of NiCrAlY coating might be one of the major contributing factors for lower erosion rate of NiCrAlY coating as compared to Ni-20Cr coating under the tested conditions. Erosion mechanisms of plasma sprayed coatings are discussed.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

A schematic view of an air jet erosion test rig

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Figure 2

Scanning electron micrograph showing silica sand particles

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Figure 3

Scanning electron micrograph showing the surface morphology of as-sprayed plasma coatings (a)NiCrAlY and (b)Ni-20Cr coating on Superfer 800H superalloy

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Figure 4

Scanning electron micrograph of as-sprayed plasma sprayed (a)NiCrAlY and (b)Ni-20Cr coatings on Superfer 800H superalloy along the cross-sectional BSEI

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Figure 5

Microhardness profiles of as-sprayed NiCrAlY and Ni-20Cr coatings with bond coat of NiCrAlY for Superfer 800H substrate along the cross section

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Figure 6

XRD of plasma-sprayed coatings on Superfer 800H superalloy. (a)NiCrAlY coating and (b)Ni-20Cr coating

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Figure 7

Macrographs of plasma spray-coated superalloys eroded at a velocity of 40ms−1 and impingement angles of 30 and 90deg. (a)NiCrAlY coating at 30deg, (b)NiCrAlY coating at 90deg, (c)Ni-20Cr coating at 30deg, and (d)Ni-20Cr coating at 90deg.

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Figure 8

Erosion rate (gg−1) against cumulative mass of erodent of plasma-sprayed coatings on Superfer 800H. (a)30deg impact angle and (b) 90deg impact angle.

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Figure 9

A histogram illustrating the steady-state erosion rate (gg−1) of the plasma-sprayed NiCrAlY and Ni-20Cr coating on Superfer 800H at 30 and 90deg impact angle

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Figure 10

Scanning electron micrographs of eroded plasma sprayed coatings (a) and (b)NiCrAlY coating, and (c) and (d)Ni-20Cr coating, at 30 and 90deg impact angle, respectively

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Figure 11

Three-dimensional optical profile of the eroded NiCrAlY and Ni-20Cr coating on Superfer 800H superalloy (a) and (b)NiCrAlY coating, and (c) and (d)Ni-20Cr coating, at a 30 and 90deg impact angle, respectively. Dimension of scanned area is 591×449μm2.

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Figure 12

Scanning electron micrographs showing cross section of Ni-20Cr coating on Superfer 800H superalloy eroded at a 90deg impact angle

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