Effect of CeO2 on the Microstructure and Properties of WC-Co-Cr Based Coatings

XU Rui; ZHANG Shuai; YIN Gaotian; LI Fei; LI Hui; LIU Shufeng; LU Fei

doi:10.16490/j.cnki.issn.1001-3660.2026.01.018

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Surface Technology ›› 2026, Vol. 55 ›› Issue (1) : 208-216. DOI: 10.16490/j.cnki.issn.1001-3660.2026.01.018

Thermal Spraying and Cold Spraying Technology

Effect of CeO₂ on the Microstructure and Properties of WC-Co-Cr Based Coatings

XU Rui, ZHANG Shuai, YIN Gaotian, LI Fei, LI Hui, LIU Shufeng, LU Fei^*

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Abstract

In the field of substrate surface strengthening technology, the use of thermal spraying processes to fabricate WC-based hard coatings is widely adopted due to its high efficiency and excellent performance. However, conventional WC-based coatings are prone to decarburization during high-temperature spraying, leading to the partial decomposition of the hard WC phase into brittle W₂C phase, which reduces the coating hardness and wear resistance, thereby limiting their service life under harsh operating conditions. To address this issue, it is imperative to optimize material composition and develop new modification technologies to enhance the overall performance of the coatings.
In this study, based on the WC-10Co-4Cr system, different mass fractions (x = 0wt.%, 1.0wt.%, 2.0wt.%, 3.0wt.%, and 4.0wt.%) of CeO₂ were introduced as a rare-earth modifier via mechanical mixing to prepare a series of CeO₂ composite WC-based spraying powders. Rare-earth-modified WC-Co-Cr-based composite coatings were fabricated on substrates through atmospheric plasma spraying (APS). The effects of CeO₂ on the microstructure, hardness, bonding strength, and wear resistance of the composite coatings were systematically investigated, and the effect of CeO₂ addition on the high-temperature decarburization behavior of the sprayed coatings was analyzed. The results indicated that the introduction of CeO₂ did not significantly alter the phase composition of the coatings, with WC remaining as the primary hard phase. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analyses revealed that CeO₂ tended to accumulate at the interlayer interfaces between WC and the Co binder phase. It interacted with Cr in the coating, forming localized agglomerations at the intersections of the lamellar structures, thereby optimizing the interfacial bonding. When the CeO₂ addition was 2.0wt.%, the coating achieved a maximum microhardness of 1 464HV0.5, representing a 42% improvement compared to the unmodified WC-10Co-4Cr coating. The bonding strength also increased from 34.9 MPa to approximately 45.0 MPa, a 28.9% enhancement, demonstrating significant mechanical performance gains.
Further analysis showed that the addition of CeO₂ effectively suppressed the high-temperature oxidation and decarburization of WC particles during spraying. Under high-temperature conditions, CeO₂ reacted with Cr to form a continuous CeO₂-Cr-WC encapsulation structure. This structure reduced the local oxygen partial pressure at the interfaces and acted as a physical barrier, significantly weakening the intensity of the W₂C diffraction peaks in X-ray diffraction patterns, indicating markedly controlled decarburization. After heat treatment, the wear mechanism of the coatings remained predominantly abrasive wear. However, the WC-10Co-4Cr-2.0wt.% CeO₂ modified coating exhibited the optimal wear resistance, with a mass loss of only 1.8 mg and a friction coefficient of 0.547. Wear surface morphology observations revealed that the modified coating surface was smoother, exhibiting only minor hard particle indentations and slight micro-cutting traces. Microcracks and delamination were significantly reduced, indicating improved structural integrity and damage resistance. In conclusion, the appropriate incorporation of CeO₂ not only significantly enhances the hardness and bonding strength of WC-based coatings but also effectively inhibits high-temperature decarburization, thereby improving wear resistance. This study demonstrates the significant potential of rare earth oxide CeO₂-modified WC-based coatings as a replacement for conventional WC-based materials in surface strengthening of critical components.

Key words

WC-Co-Cr / CeO₂ modification / plasma spraying / heat treatment / wear resistance

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XU Rui, ZHANG Shuai, YIN Gaotian, LI Fei, LI Hui, LIU Shufeng, LU Fei. Effect of CeO₂ on the Microstructure and Properties of WC-Co-Cr Based Coatings[J]. Surface Technology. 2026, 55(1): 208-216

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