研究一种新型镍基合金X-1#在550 ℃, 23 MPa含PO₄^3-, Cl^-和SO₄^2-超临界水中分别腐蚀72, 159, 248, 429和537 h的腐蚀特性. 结合SEM, EDS, XRD和XPS等分析测试方法研究了X-1#合金氧化膜和反应釜沉积物的形貌、物相组成和元素成分分布等. 结果表明, X-1#合金在该环境下形成了均匀和完整的氧化膜, 氧化膜由疏松外层和致密内层组成, 外层主要包含NiO, Ni(OH)₂和磷酸盐, 内层由NiCr₂O₄和Cr₂O₃组成. 腐蚀初始阶段腐蚀速率较快, 248 h后腐蚀速率明显下降, 这是由于氧化膜内层稳定性好且连续致密分布, 有利于X-1#合金抗高温氧化腐蚀.

The productivity of municipal sewage sludge is difficult to treat by traditional methods. Supercritical water oxidation (SCWO) is an attractive municipal sewage sludge treatment technology. However, the process of SCWO must be carried out in a reactor which will resist not only high temperature (above 374.15 ℃) and high pressure (above 22.1 MPa) conditions but also a corrosive environment. Thus, the material used in the equipment is referred to be a key factor that restricts the application of the SCWO technology. Many materials have been selected for corrosion test under corrosive environments with SCWO, including austenitic stainless steel, nickel base alloys, titanium alloys and zirconium alloys. At present, in order to treat rich phosphorous sewage sludge, a new corrosion resistant nickel base alloy X-1# alloy has been developed to apply to the reactor of SCWO process. X-1# alloy has excellent corrosion-resistance and oxidation-resistance properties in supercritical water containing PO₄^3-, Cl^- and SO₄^2-. The corrosion behaviors of X-1# alloy exposed to 550 ℃, 23 MPa supercritical water containing PO4^3-, Cl^- and SO₄^2- were investigated in this research. The exposed time was 72, 159, 248, 429 and 537 h. Morphologies, microstructures and chemical composition of oxide films in X-1# alloy and deposit sediment in reaction were studied using grazing incidence XRD, XPS and SEM equipped with EDS. The XRD, EDS and XPS analysis of X-1# alloy was performed to identify the composition of oxide layers, which were identified as NiCr₂O₄, Cr₂O₃, NiO, Ni₃(PO₄)₂, CrPO₄ and Na₃PO₄. In addition, it was founded that continuous and uniform oxide films were formed in supercritical water. The oxide film was a duplex-layer structure, the loose outer layer was NiO, Ni(OH)₂ and phosphates, including Ni₃(PO₄)₂, CrPO₄ and Na₃PO₄, while the compact inner layer consisted of NiCr₂O₄ and Cr₂O₃. X-1# alloy showed a high corrosion rate in the initial stage and the corrosion rate decreased obviously after exposed to 248 h, the reason of which was that the compact inner layer of oxide films had good stability and benefited to the corrosion behavior of X-1# alloy. In order to explain the corrosion behavior of X-1# alloy, the oxide films growth mechanical, metal ions and oxygen ions dissolution mechanism and phosphates precipitation mechanism will be discussed in this research.