Microstructure and Properties of HVOF-Sprayed WC-(W,Cr)2C-Ni Coatings

Abstract

The composition WC-(W,Cr) 2 C-Ni is one of the standard compositions used for the preparation of thermally sprayed coatings by high velocity oxy-fuel (HVOF) spraying. Surprisingly, this composition has been poorly investigated in the past. Frequent use of commercial designations WC-ÔCrCÕ-Ni, WC-Cr 3 C 2 -Ni, and WC-NiCr indicates the insufficient knowledge about the phase compositions of these powders and coatings. The properties of these coatings differ significantly from those of WC-Co and WC-CoCr coatings. In this paper, the results of different series of experiments conducted on HVOFsprayed WC-(W,Cr) 2 C-Ni coatings are compiled and their specific benefits pointed out. The focus of this study is on the analysis of the microstructures and phase compositions of the feedstock powders and coatings. Unlike WC-Co and Cr 3 C 2 -NiCr, WC-(W,Cr) 2 C-Ni is not a simple binary hard phase-binder metal composite. The phase (W,Cr) 2 C with unknown physical and mechanical properties appears as a second hard phase, which is inhomogeneously distributed in the feedstock powders and coatings. As examples of coating properties, the oxidation resistance and dry sliding wear properties are compared with those of WC-10%Co-4%Cr coatings.

The Instrumented Indentation Study of HVOF-Sprayed Hardmetal Coatings

“…1. Detailed characterization of their microstructure can be found elsewhere (Ref 31,32,34,35); their basic mechanical properties are summarized in Table 2.…”

Binary WC- and Cr3C2-containing hardmetal compositions for thermally sprayed coatings

“…Currently, there are variations in contents of the components in the range of 1-4 % from different manufacturers [2,3]. The composition contains a lower binder metal content than other WC-based compositions but can be sprayed with a high deposition efficiency [15,16].…”

“…The metallurgical processes during feedstock powder preparation and spraying for this composition have been studied in detail only recently [11,15,16]. The most specific feature is the formation of (W,Cr)2C.…”

“…The occasional absence or occurrence of (W,Cr)2C might be one reason why the feedstock powders of this composition are currently traded with different designations such as WC-'CrC'-Ni, WC-'Cr3C2'-Ni or WC-NiCr [2,15,16].…”

Evaluation of Thermocyclic Oxidation Behavior of HVOF Sprayed WC-CrC-Ni Coatings

“…Lutz-Michael Berger et al [12] reported that WC-(W,Cr)2C-Ni coatings are having much superior oxidation and corrosion resistance to that of other commercial WCbased coatings and discussed that the composition WC-(W,Cr)2C-Ni can bridge the gap between WC-Co and Cr3C2-NiCr with regard to oxidation and corrosion resistance.…”