Abstract High velocity oxy-fuel (HVOF) thermal spray process has shown obvious advantages over other surface hardening techniques when depositing WC-based layers, such as the laser cladding, electrodeposition and chemical/physical vapour deposition (CVD/PVD) methods, due to its versatility, survivability of hardening phase and low cost. HVOF thermal sprayed WC-based coatings are widely used in components that operate in harsh environments needing excellent sliding, fretting, abrasion and erosion resistance. WC-CrxCy-Ni coating shows better wear performance than the WC-Co-Cr coating at high temperature but inferior wear performance at room temperature at lower loads according to literature; however, the wear performance and relevant mechanisms of these two coatings under higher loads has not been reported. To fill this knowledge gap, wear testing of HVOF thermal sprayed WC-CrxCy-Ni and WC-Co-Cr coatings under high loads (96, 240 and 318 N) against a sintered WC-Co (6 mm diameter ball) counter-body was studied in this paper. For WC-CrxCy-Ni coating, decarburization of CrxCy rather than WC, took place during spraying. While the decarburization of WC to W2C occurred in the WC-Co-Cr coating. The major hardening phase (WC) dominated the wear performance of the coatings given its high hardness and small size, and Co also appeared to be a superior binder phase than Ni. At the maximum load, the specific wear rate of WC-CrxCy-Ni coating against WC-Co counter body was 17.92 × 10-7 mm3 N-1m-1, which is two times that of WC-Co-Cr coating (9.81 × 10-7 mm3 N-1m-1). The wear mechanisms for WC-CrxCy-Ni coatings included abrasion of the matrix, cracking of the secondary carbide phase and pulling out of WC particles. For WC-Co-Cr coatings, abrasion of the matrix was marginal, and cracking of the secondary carbide was not observed. The presence of CrxCy of lower hardness than the WC decreased the wear resistance of entire WC-based coating at room temperature, and improved oxidation resistance of WC at high temperatures due to the higher affinity of Cr to O. Hence, the secondary carbide hardening phase may be detrimental when considering the wear applications of HVOF thermal sprayed WC-based coatings.

中文翻译：

---

HVOF热喷涂WC-Co-Cr和WC-CrxCy-Ni涂层的干滑动磨损行为

摘要 高速氧燃料 (HVOF) 热喷涂工艺在沉积 WC 基层时表现出明显优于其他表面硬化技术，如激光熔覆、电沉积和化学/物理气相沉积 (CVD/PVD) 方法，这是由于其通用性、硬化阶段的生存能力和低成本。HVOF 热喷涂 WC 基涂层广泛用于在恶劣环境中运行需要出色的滑动、微动、磨损和侵蚀性的部件。根据文献报道，WC-CrxCy-Ni涂层在高温下的耐磨性能优于WC-Co-Cr涂层，但在室温下较低载荷下的耐磨性能较差；然而，这两种涂层在较高载荷下的磨损性能和相关机制尚未见报道。为了填补这一知识空白，本文研究了 HVOF 热喷涂 WC-CrxCy-Ni 和 WC-Co-Cr 涂层在高载荷（96、240 和 318 N）下对烧结 WC-Co（直径为 6 毫米的球）配对体的磨损测试。对于 WC-CrxCy-Ni 涂层，在喷涂过程中发生的是 CrxCy 而不是 WC 的脱碳。而WC-Co-Cr涂层发生WC脱碳为W2C。鉴于其高硬度和小尺寸，主要硬化相 (WC) 主导了涂层的磨损性能，并且 Co 似乎也是比 Ni 更好的结合相。在最大载荷下，WC-CrxCy-Ni 涂层对 WC-Co 反体的比磨损率为 17.92 × 10-7 mm3 N-1m-1，是 WC-Co-Cr 涂层（9.81 × 10-7 mm3 N-1m-1)。WC-CrxCy-Ni 涂层的磨损机制包括基体磨损、二次碳化物相的开裂和 WC 颗粒的拉出。对于 WC-Co-Cr 涂层，基体的磨损很小，并且没有观察到二次碳化物的开裂。硬度低于 WC 的 CrxCy 的存在降低了整个 WC 基涂层在室温下的耐磨性，并且由于 Cr 与 O 的亲和力更高，因此提高了 WC 在高温下的抗氧化性。 因此，二次碳化物硬化相在考虑 HVOF 热喷涂 WC 基涂层的磨损应用时，这可能是不利的。