کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
283932 | 1430649 | 2008 | 5 صفحه PDF | دانلود رایگان |
The oxidation and lower temperature hot corrosion (LTHC) processes occurring on the surface of Ni-Cr coatings produced by high velocity arc spray (HVAS) were studied. Several different conditions were studied under simulated boiler conditions at 650°C. The protection effect of an Al coating deposited by HVAS onto the Ni-Cr coating was also investigated. Microscope, X-ray diffraction and corrosion rate curves have been used to analyze corrosion mechanisms. The experimental results show that: 1) The oxidation rates are almost superposed in both air (no SO3) and in simulated coal-fired gas (containing SO3) as long as no salt was present on the surface. These rate curves show a logarithmic relationship. 2) When the surface is coated with salt (75%K2SO3 + 25%Na2SO3) the rate curve for LTHC of the Ni-Cr coated surface shows a parabolic shape in the simulated coal-fire flue gas. In air only the oxidation reaction takes place, the second type of LTHC was not seen. And 3) the Al over coating on the Ni-Cr enhances resistance to LTHC because an inter-metallic compound, Al3Ni2, forms at the Al/Ni-Cr interface and because of the increase in coating thickness.
Journal: Journal of China University of Mining and Technology - Volume 18, Issue 3, September 2008, Pages 444-448