NiCr-Cr3C_(2)-ZrO_(2)-BaF_(2)·CaF_(2)涂层高温摩擦磨损性能

High Temperature Tribological Properties of NiCr-Cr3C_(2)-ZrO_(2)-BaF_(2)·CaF_(2) Coating

为提高 NiCr-Cr_(3)C_(2)-BaF_(2)·CaF_(2) 涂层高温耐摩擦磨损性能,减少热喷涂过程中润滑相 BaF_(2)·CaF_(2) 火焰烧蚀,采用溶胶凝胶方法将 BaF_(2)·CaF_(2) 粉体以弥散形式包覆于抗烧蚀陶瓷相 ZrO_(2) 内,形成 ZrO_(2)-BaF_(2)·CaF_(2) 抗烧蚀包覆型粉体,将粉体与 NiCr-Cr_(3)C_(2)混合后爆炸喷涂以提高涂层内 BaF_(2)·CaF_(2)含量,并表征涂层微观组织和高温耐磨损性能。结果表明:ZrO_(2)包覆型粉体中 BaF_(2)·CaF_(2)呈弥散式分布,制备的 NiCr-Cr_(3)C_(2)-ZrO_(2)-BaF_(2)·CaF_(2)涂层相比传统 NiCr-Cr_(3)C_(2)-BaF_(2)·CaF_(2)涂层,Ca、Ba 元素含量均提升 1 倍以上,两涂层显微硬度分别为 1 041 HV 和 690 HV,这说明 ZrO_(2)陶瓷包覆能有效减少 BaF_(2)·CaF_(2)在喷涂过程中的高温烧蚀,且大幅提升了涂层硬度。高温摩擦磨损试验结果显示,NiCr-Cr_(3)C_(2)-ZrO_(2)-BaF_(2)·CaF_(2) 涂层在 600 ℃、 700 ℃和 800 ℃时的平均摩擦因数分别为 0.25、0.17 和 0.18,与 NiCr-Cr_(3)C_(2)-BaF_(2)·CaF_(2)涂层相比分别降低了 16.7%、39.3% 和 5.3%;NiCr-Cr_(3)C_(2)-ZrO_(2)-BaF_(2)·CaF_(2)涂层磨损率为 5.47×10^(-6)mm^(3) ·N^(-1) ·m^(-1),较 NiCr-Cr_(3)C_(2)-BaF_(2)·CaF_(2)涂层降低了 38.6%。 对磨球表面的微观表征显示,涂层中润滑相含量提升使 NiCr-Cr_(3)C_(2)-ZrO_(2)-BaF_(2)·CaF_(2) 涂层在对磨球表面形成更为完整的润滑转移膜,这将有利于涂层的高温润滑性、稳定性和耐磨损性能。研究结果对热喷涂粉体中易烧蚀物相的热防护和高温自润滑耐磨涂层性能的提升具有借鉴意义。

Aiming to improve the friction and wear resistance of NiCr-Cr_(3)C_(2)-BaF_(2)·CaF_(2) coating at high temperature and reduce the burn out of the self-lubricating component BaF_(2)·CaF_(2) during thermal spraying, the sol-gel method is used to disperse the BaF_(2)·CaF_(2) powder in ZrO_(2) microspheres. Then, the ZrO_(2)-BaF_(2)·CaF_(2) powder is mixed with the NiCr-Cr_(3)C_(2) powder and then sprayed by a detonation gun to prepare coating samples. The microstructure, high-temperature friction and wear resistance of the coatings are studied. Results show that: BaF_(2) · CaF_(2) powder can homogeneously disperse in ZrO_(2) coated powder. Comparing the NiCr-Cr_(3)C_(2)-BaF_(2)·CaF_(2) coating with the present NiCr-Cr_(3)C_(2)-ZrO_(2)-BaF_(2)·CaF_(2) coating, the elements of Ca and Ba in the latter are increased by more than one times, and the microhardness of the two coatings is 690 HV and 1041 HV, respectively. Therefore, it can be concluded that the ZrO_(2) coating can effectively reduce BaF_(2)·CaF_(2) ablation during the spraying process and enormously improve the hardness of the coating. The average friction factor of NiCr-Cr_(3)C_(2)-ZrO_(2)-BaF_(2)·CaF_(2) coating is 0.25, 0.17 and 0.18 at 600 ℃, 700 ℃ and 800 ℃, respectively. Compared with the NiCr-Cr_(3)C_(2)-BaF_(2)·CaF_(2) coating, the friction factor is reduced by 16.7%, 39.3% and 5.3% at 600 ℃ , 700 ℃ and 800 ℃ , respectively. The wear rate of NiCr-Cr_(3)C_(2)-ZrO_(2)-BaF_(2) · CaF_(2) coating is 5.47×10-6 mm^(3) ·N-1 ·m-1 , which is 38.6% lower than that of NiCr-Cr_(3)C_(2)-BaF_(2)·CaF_(2) coating. The microscopic characterization of the worn surface of the grinding ball shows that the increment of the lubricating phase in the coating makes the NiCr-Cr_(3)C_(2)-ZrO_(2)-BaF_(2)·CaF_(2) coating form a broader lubricating transfer film on the surface of the grinding ball, which will benefit the high-temperature lubricity, stability and wear resistance of the coating. The results can be used as a reference for the thermal protection of ablation phase in thermal spraying powder and the improvement of the performance of high temperature self-lubricating wear-resistant coating.