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68Ni18Cr6WMoAlTi是一种不含钴的镍基铸造合金。合金的高温综合力学性能与目前广泛使用的U—500合金相当,可用做燃气轮机叶片材料。本文着重比较了新合金与U—500合金的热腐蚀性能。合金的热腐蚀试验使用盐淋浴装置和单管燃烧装置,在高温850℃混合盐中研究合金的热腐蚀。测量合金试样的失重,平均穿透深度和金属损失。使用光学显微镜、电子显微镜、扫描电镜、能谱和x射线衍射研究了热腐蚀过程中产生的氧化皮和硫化物。试验结果表明:68Ni18Cr6WMoAlTi合金抗热腐蚀能力优于U—500合金。盐淋浴200小时合金的失重为17.8mg/cm~2,而U—500合金的失重为134.3mg/cm~2。合金的平均穿透深度只有U—500合金的1/4。尤为明显的是68Ni18Cr6WMoAlTi合金的金属损失很少。试验发现两种合金的表面硫化层中硫化物成份不同。68Ni18Cr6WMoAlTi合金生成富Ti的硫化物,在氧化过程中更稳定,可以推迟硫化/氧化过程。
68Ni18Cr6WMoAlTi is a cobalt-free nickel-based cast alloy. Alloy high temperature mechanical properties and U-500 alloy currently widely used, can be used as gas turbine blade material. This article focuses on comparing the hot corrosion properties of the new alloy with the U-500 alloy. The alloy hot corrosion test using salt shower and single tube combustion device, at a high temperature of 850 ℃ mixed salt to study the hot corrosion of the alloy. The alloy specimens were measured for weight loss, average penetration depth, and metal loss. Oxides and sulfides produced during hot etching were investigated using light microscopy, electron microscopy, scanning electron microscopy, energy dispersive spectroscopy and x-ray diffraction. The experimental results show that the corrosion resistance of 68Ni18Cr6WMoAlTi alloy is better than U-500 alloy. Salt bath 200 hours weight loss of alloy 17.8mg / cm ~ 2, and U-500 alloy weight loss of 134.3mg / cm ~ 2. The average penetration depth of alloy is only 1/4 of U-500 alloy. It is particularly obvious that the metal loss of the 68Ni18Cr6WMoAlTi alloy is very small. It was found that the sulphides in the surface sulphide layers of the two alloys were different. The 68Ni18Cr6WMoAlTi alloy generates Ti-rich sulfides, which are more stable during the oxidation process and can delay the sulfidation / oxidation process.