Effect of Particle and Carbide Grain Sizes on a HVOAF WC-Co-Cr Coating for the Future Application on Internal Surfaces: Microstructure and Wear

J Pulsford, S Kamnis, J. Murray, Mingwen Bai, T. Hussain

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Abstract

The use of nanoscale WC grain or finer feedstock particles is a possible method of improving the performance of WC-Co-Cr coatings. Finer powders are being pursued for the development of coating internal surfaces, as less thermal energy is required to melt the finer powder compared to coarse powders, permitting spraying at smaller standoff distances. Three WC-10Co-4Cr coatings, with two different powder particle sizes and two different carbide grain sizes, were sprayed using a high velocity oxy-air fuel (HVOAF) thermal spray system developed by Castolin Eutectic-Monitor Coatings Ltd., UK. Powder and coating microstructures were characterized using XRD and SEM. Fracture toughness and dry sliding wear performance at three loads were investigated using a ball-on-disk tribometer with a WC-Co counterbody. It was found that the finer powder produced the coating with the highest microhardness, but its fracture toughness was reduced due to increased decarburization compared to the other powders. The sprayed nanostructured powder had the lowest microhardness and fracture toughness of all materials tested. Unlubricated sliding wear testing at the lowest load showed the nanostructured coating performed best; however, at the highest load this coating showed the highest specific wear rates with the other two powders performing to a similar, better standard.
Original languageEnglish
Pages (from-to)207–219
Number of pages13
JournalJournal of Thermal Spray Technology
Volume29
Early online date1 Dec 2017
DOIs
Publication statusPublished - Jan 2018
Externally publishedYes

Bibliographical note

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.

Keywords

  • ball-on-disk wear
  • HVOF
  • internal spray
  • WC-Co-Cr

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