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. 2022 Aug 11;15(16):5537.
doi: 10.3390/ma15165537.

Influence of WC Particle Size on the Mechanical Properties and Residual Stress of HVOF Thermally Sprayed WC-10Co-4Cr Coatings

Kunyang Fan  1   2 , Wenhuang Jiang  1   2 , Vladimir Luzin  3   4 , Taimin Gong  5 , Wei Feng  1   2 , Jesus Ruiz-Hervias  6 , Pingping Yao  5
Affiliations

Influence of WC Particle Size on the Mechanical Properties and Residual Stress of HVOF Thermally Sprayed WC-10Co-4Cr Coatings

Kunyang Fan et al. Materials (Basel). .

Abstract

Cermet coatings deposited using high-velocity oxy-fuel (HVOF) are widely used due to their excellent wear and corrosion resistance. The new agglomeration-rapid sintering method is an excellent candidate for the preparation of WC-Co-Cr feedstock powders. In this study, four different WC-10Co-4Cr feedstock powders containing WC particles of different sizes were prepared by the new agglomeration-rapid sintering method and deposited on steel substrates using the HVOF technique. The microstructures and mechanical properties of the coatings were investigated using scanning electron microscopy, X-ray diffraction, nanoindentation, and Vickers indentation. The through-thickness residual stress profiles of the coatings and substrate materials were determined using neutron diffraction. We found that the microstructures and mechanical properties of the coatings were strongly dependent on the WC particle size. Decarburization and anisotropic mechanical behaviors were exhibited in the coatings, especially in the nanostructured coating. The coatings containing nano- and medium-sized WC particles were dense and uniform, with a high Young's modulus and hardness and the highest fracture toughness among the four coatings. As the WC particle size increased, the compressive stress in the coating increased considerably. Knowledge of these relationships enables the optimization of feedstock powder design to achieve superior mechanical performance of coatings in the future.

Keywords: WC–10Co–4Cr; mechanical property; residual stress; thermal spray.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 6
Figure 6
W2C formation and fragmentation of the WC phases in the coatings: (a) B1; (b) B2.
Figure 1
Figure 1
Morphology of the WC, Co, and Cr starting powders: (a) nano WC, (b) medium WC, (c) coarse WC, (d) Co, (e) Cr.
Figure 2
Figure 2
The morphologies and cross-sections of the four studied WC–10Co–4Cr spraying feedstock powders: (a,b) N; (c,d) B1; (e,f) M and (g,h) B2.
Figure 3
Figure 3
XRD patterns of the WC–10Co–4Cr feedstock powders (a) and the coatings (b).
Figure 4
Figure 4
Cross-sectional BSE–SEM images of the studied WC–10Co–4Cr coatings: (a) N; (b) B1; (c) M; (d) B2.
Figure 5
Figure 5
Schematic of the formation of the lamellar-like structures in HVOF sprayed WC–10Co–4Cr coatings with different WC particle sizes: (a) N; (b) B1; (c) M; (d) B2.
Figure 7
Figure 7
The typical SEM micrographs of nanoindentation imprint on the coatings: (a) N; (b) M.
Figure 8
Figure 8
Young’s modulus (E) and nanohardness (H) vs. penetration depth (h) curves on the coating surfaces. (a) Young’s modulus; (b) nanohardness.
Figure 9
Figure 9
The through-thickness distributions of the Young’s modulus (E) and hardness (H) in the coatings. (a) The Young’s modulus; (b) the hardness.
Figure 10
Figure 10
The typical SEM morphology of Vickers indentation imprints on the cross-sections of the studied WC–10Co–4Cr coatings: (a) N; (b) B1; (c) M; (d) B2.
Figure 11
Figure 11
Typical indentation crack profiles in the studied WC–10Co–4Cr coatings: (a) N; (b) B1; (c) M; (d) B2.
Figure 12
Figure 12
Stress distributions in the four WC–10Co–4Cr coating/steel substrate samples. Symbols with error bars represent experimental data, while lines correspond to an empirical model fitting the data sets. (a) N; (b) B1; (c) M; (d) B2.
Figure 13
Figure 13
Decomposition of the total residual stress into the two components, the thermal mismatch stress and the deposition stress, for the coatings with different WC grain sizes.
See this image and copyright information in PMC

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