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合金粉末(A合金)、Fe-16Cr-30Mo-4C-2B合金粉末(B合金)和Fe-16Cr-30Mo-2C-1B-7P合金粉末(C合金)。采用大气等离子喷涂(APS)和高速火焰喷涂(HVOF)工艺在低碳钢表面制备了这些合金涂层。所有合金均采用超音速火焰喷涂技术获得了完美的非晶态涂层。而APS工艺仅从合金B和C获得了理想的非晶态涂层。从1N HCl溶液中的阳极极化曲线可以看出，合金A的涂层的电流密度接近于合金B和C的涂层的电流密度。因此，人们认为所有合金的涂层耐蚀性几乎是一样的。经盐酸溶液浸泡试验，A合金APS涂层的耐蚀性与SUS316L钢板相当。而B、C合金的APS涂层的腐蚀速率是A合金的1/100，因此B、C合金涂层的耐蚀性较好。A、B、C合金的回火涂层由铁素体、M&lt；23&gt；C6、M_7C_3碳化物和M_3P磷化物、铁素体、M&lt；23&gt；(C，B)_6、M7(C，B)_3碳化物和铁素体、M_&lt；23&gt；(C，B)_6，M_7(C，B)_3和M_3P磷化物。透射电子显微镜观察发现，晶化处理后的B合金涂层中形成了直径为10 nm的细晶组织。C合金的超音速火焰喷涂涂层在973K回火100h后仍保持纳米结构。回火涂层的耐酸腐蚀性能低于喷涂层。但结果表明，回火涂层的耐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.