The present study investigates the initial corrosion behaviour of HVAF-sprayed NiCr, NiAl and NiCrAlY coatings in two different environments, O2 + H2O and O2 + H2O + KCl at 600 °C for up to 168 h in order to evaluate the possibility of utilizing such coatings in biomass- and waste-fired boilers. SEM/EDX analysis showed that all coatings displayed a protective behaviour in O2 + H2O. Upon addition of KCl (O2 + H2O + KCl), the corrosion behaviour of the NiCr coating drastically changed as it formed a thick oxide layer and displayed major chlorine diffusion down to the substrate. The NiCrAlY coating displayed a significantly better corrosion resistance with only minor oxide formation. The NiAl coating exhibited a protective behaviour similar to when exposed in the absence of KCl indicating that a thin protective oxide has formed on the coating surface. The performance of the NiAl and NiCrAlY coatings is promising for future studies with long-term exposures in more corrosive environments such as in a biomass- and waste-fired boiler.

中文翻译：

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用于锅炉应用的 HVAF 喷涂镍基涂层的高温腐蚀

本研究调查了 HVAF 喷涂的 NiCr、NiAl 和 NiCrAlY 涂层在两种不同环境中的初始腐蚀行为，O2 + H2O 和 O2 + H2O + KCl 在 600 °C 下长达 168 小时，以评估使用这种涂层的可能性。生物质和废物燃烧锅炉中的涂层。SEM/EDX 分析表明，所有涂层在 O2 + H2O 中都表现出保护行为。添加 KCl (O2 + H2O + KCl) 后，NiCr 涂层的腐蚀行为发生了巨大变化，因为它形成了厚厚的氧化层，并显示出大量的氯向下扩散到基材。NiCrAlY 涂层显示出明显更好的耐腐蚀性，仅形成少量氧化物。NiAl 涂层表现出类似于在没有 KCl 的情况下暴露时的保护行为，表明在涂层表面形成了薄的保护性氧化物。