Formation of Super-Corrosion Resistant Bulk Amorphous Alloy Coatings by Thermal Spraying and Properties of Coatings Having Nano-Structure after Crystallization

制备了Fe-10Cr-10Mo-2C-8P（合金A）、Fe-16Cr-30Mo-4C-2B（合金B）和Fe-16Cr-30Mo-2C-1B-7P（合金C）合金粉末进行热喷涂。采用大气等离子喷涂（APS）和高速火焰喷涂（HVOF）工艺在低碳钢基体上制备了这些合金的涂层。采用HVOF工艺对所有合金均获得了完美的非晶态镀层。从HVOF涂层在1N HCl溶液中的阳极极化曲线看，合金a涂层的电流密度与合金B和合金C涂层的电流密度接近。因此，人们认为所有合金镀层的耐蚀性几乎是相同的。A合金APS涂层在HCl溶液中的耐蚀性与SUS316L板相同。另一方面，B和C合金涂层的耐蚀性很好，因为B和C合金的APS涂层的腐蚀速率是A合金的1/100。A、B和C合金的回火涂层分别由铁素体、M_<23>(C，B)_6、M_7(C，B)_3硼碳化物和铁素体、M_<23>(C，B)_6、M_7(C，B)_3硼碳化物和M_3P磷化物组成。TEM观察发现，B合金涂层结晶后形成了直径为10nm的细晶组织。C合金的HVOF涂层在973K下回火100h后仍能保持纳米结构。在耐盐酸溶液中，回火涂层的耐腐蚀性不如喷涂涂层。结果表明，回火涂层的耐盐酸性能优于镍基自熔合金涂层。

Alloy powders of Fe-10Cr-10Mo-2C-8P (alloy A), Fe-16Cr-30Mo-4C-2B (alloy B) and Fe-16Cr-30Mo-2C-1B-7P (alloy C) were made for thermal spraying. The coatings of these alloys were prepared on the mild steel substrate by atmospheric plasma spraying(APS) and high velocity flame spraying(HVOF) processes. Perfect amorphous coatings were obtained by the HVOF process from all alloys. Whereas, the perfect amorphous coatings were obtained by the APS process from only alloy B and C. The current density of the coating of alloy Awas close to that of the coatings of alloys B and C from the anodic polarization curves of the HVOF coatings in 1N HCl solution. Therefore, it was thought that the corrosion resistance of the coatings of all alloys was almost the same. The corrosion resistance of the APS coating of alloy A was the same as SUS316L plate from the immersion test in HCl solution. On the other hand, the corrosion resistance of the coatings of alloys B and C was excellent, because the corrosion rate of the APS coatings of alloys B and C was 1/100 of that of the alloy A. The tempered coatings of alloys A,B,and C were composed of ferrite, M_<23>C_6,M_7C_3 carbides and M_3P phosphide, ferrite, M_<23>(C,B)_6, M_7(C,B)_3 borocarbides and ferrite, M_<23>(C,B)_6,M_7(C,B)_3 borocabides and M_3P phosphide, respectively. It was recognized that the fine-grained structure of 10nm in diameter was formed in the coating of alloy B after crystallization from TEM observation. Also, the HVOF coating of alloy C held the nano-structure after tempered at 973K for 100h. The corrosion resistance of the tempered coatings was inferior to that of the as-sprayed coatings in resistant to hydrochloric acid solution. However, it was showed that the tempered coatings were superior to nickel-based self-fluxing alloy coating in resistant to hydrochloric acid solution.