A Comparison of Mechanical and Tribological Behavior of Nanostructured and Conventional WC-12Co Detonation-Sprayed Coati
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JTTEE5 22:478–490 DOI: 10.1007/s11666-013-9901-3 1059-9630/$19.00 ASM International
A Comparison of Mechanical and Tribological Behavior of Nanostructured and Conventional WC-12Co Detonation-Sprayed Coatings Suresh Babu Pitchuka, Bikramjit Basu, and G. Sundararajan (Submitted June 11, 2012; in revised form December 4, 2012)
In the present study, WC-12Co coatings were deposited by detonation-spraying technique using conventional and nanostructured WC-12Co feedstock at four different oxy/fuel ratios (OF ratio). The coatings exhibited the presence of phases like W2C and W due to the decarburization of the WC phase, and the proportions of these phases were higher in the nano WC-12Co coatings compared with conventional WC-12Co coatings. Coating hardness and fracture toughness were measured. The tribological performance of coatings was examined under dry sand rubber wheel abrasion wear, and solid particle erosion wear conditions. The mechanical and wear properties of coatings were influenced by degree of decarburization and more so in the case of nanostructured WC-Co coatings. The results indicate that the extent of decarburization has a substantial influence on the elastic modulus of the coating which in turn is related to the extent of intersplat cracking of the coating.
Keywords
decarburization, thermal-spray coatings, three body abrasion, solid particle erosion, WC-12Co
1. Introduction Thermal-sprayed WC-12Co coatings have been widely employed on several industrial components where high resistance to wear is required. Several thermal-spray techniques, such as air and vacuum plasma spray, highvelocity oxy-fuel (HVOF), and detonation spray (DS), have been utilized to deposit the WC-Co coatings (Ref 1-8). In most of the earlier studies, the feedstock utilized for thermal spraying has been the conventional WC-Co powder composed of WC cuboids of several micrometers in size (Ref 9). However, studies on bulk WC-Co cermets obtained by liquid phase sintering have indicated that the reduction in WC cuboids to submicron and nanometer levels (i.e., using nanostructured powders as feedstock) improves the hardness and tribological performance (Ref 10-12). In view of the above, there has been a natural drive toward the introduction of nanostructured WC-Co powders as the feedstock for thermalspray coatings (Ref 13).
Suresh Babu Pitchuka, ARC International, Balapur, Hyderabad, Andhra Pradesh, India; Bikramjit Basu, Indian Institute of Science—Materials Research Centre, Bangalore, India; and G. Sundararajan, ARC International, Balapur, Hyderabad, Andhra Pradesh, India. Contact e-mail: [email protected].
478—Volume 22(4) April 2013
However, the results with regard to nanostructured WC-Co coatings have been mixed. One consistent observation has been that the extent of decarburization of WC (to form W2C and W phases) increases as one goes from the use of conventional to nanostructured WC-Co as feedstock irrespective of the thermal-spray technique used (Ref 3, 6-8, 14-16) and in the extreme, can lead to amorphization of the Co
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