Microstructure and Properties Characterization of WC-Co-Cr Thermal Spray Coatings

Abstract

WC-Co-Cr coatings are widely employed due to their improved wear resistance and mechanical properties, however, the properties and performance of these coatings are compromised by the processing parameters of each spraying technique. Therefore, this study is aimed to evaluate and determine the effect of the deposition parameters on the properties and microstructural characteristics of WC-Co-Cr coatings using a more economical thermal spray technique. In particular, the influence of flame spray parameters on the microstructure, crystal structure, hardness, and sliding wear resistance of WC-Co-Cr coatings was examined. Two parameters were considered: Type of flame (reducing, neutral and oxidizing), and the spray torch nozzle exit area. Results indicated that WC particles undergo considerable degree of decarburization and dissolution during spraying, showing substantial amounts of W 2 C, W, and Co 3 W 3 C, for all the considered conditions. However, the extent of phase transformation depended largely on the flame chemistry. The microstructure of the coatings was mainly affected by the spray nozzle. Regarding the sliding wear behavior, the coatings with uniform distribution of hard particles provided the best wear resistance. The decomposition of WC into W 2 C phase seems to have meaningless significance in the mass loss, nevertheless, the WC phase transformation to metallic tungsten and η-phase (Co 3 W 3 C) produce higher wear rates due to deficiency of carbide particles and embrittlement of the binder phase which induces cracking and delamination of the splats.

Comparative Analysis of Mechanical Properties of WC-based Cermet Coatings Sprayed by HVOF onto AZ31 Magnesium Alloy Substrates

“…Especially WC-based powders are widely used as they are characterized by a very high hardness compared to most cermets, and addition of, for example, Cr and Co as binding ingredients improves their strength and provides better coatings adhesion. In the case of sprayed coatings from Cr 3 C 2 -NiCr powders, plastic NiCr phase is the matrix, and the reinforcement is hard Cr 3 C 2 particles, which are resistant to abrasion [20][21][22][23][24].…”

Erosive and corrosive wear performance and characterization studies of plasma‐sprayed WC/Cr 3 C 2 coating on SS316

“…The presence of the hard phase dispersed in the microstructure was a key factor for conferring superior wear resistance despite the presence of the relatively higher pores. 8,13…”

“…WC-Co-based coatings protected the steel substrates from wet and dry abrasion conditions and also observed that finer WC particles were associated with increased wear resistance. [6][7][8][9][10][11] Jonda et al 12 and Mendez-Medrano et al 13 evaluated the microstructure and phase characterization of tungsten carbide and chromium carbide coatings. They noticed that the X-ray diffractometry (XRD) pattern of the coatings indicated the WC and Cr 3 C 2 decarburization phases and disintegration of WC particles occurs, resulting in substantial amounts of W 2 C, W, and Co 3 W 3 C. Schwetzke et al 14 and Matikainen et al 15 investigated the microstructure of WC-based coatings on mild steel substrates.…”

“…Jonda et al 12 . and Mendez‐Medrano et al 13 . evaluated the microstructure and phase characterization of tungsten carbide and chromium carbide coatings.…”

Effect of the Average Energy on WC Grain Growth of WC-10Co-4Cr Composite by Laser Cladding

“…WC-10Co-4Cr composite or alloy is widely used for coating applications in aeronautics, mining, construction, and heavy machinery industries [1,2]. In general, WC-Co-Cr based coatings are characterized by having high hardness and high wear, erosion, and corrosion resistance [3,4].…”