本文以喷射盐水溶液的“HCF”全自动热腐蚀疲劳直接对比试验法,研究了4 Cr10Si2Mo.18SR、20—14三种耐热钢与Co—50、Ni—81两种合金涂层的抗热腐蚀疲劳性能。腐蚀程度的测量由合金的最大腐蚀深度来决定,并以金相、电子探针和X-光衍射技术研究了各钢种的热腐蚀疲劳破坏过程和两种涂层有效地抗热腐蚀疲劳的原因。在“HCF”热腐蚀疲劳试验条件下我们发现:①耐热钢具有三带侵蚀构造。疏松的腐蚀产物层层开裂脱落,毫无保护作用,硫与氧直接向合金内部侵入,氧甚至比硫侵入得更深。②耐热钢热腐蚀疲劳破坏的程度主要与合金内部侵蚀带的侵蚀类型有关。③无论Ni—基或Co—基合金涂层均能生成致密的抗热腐蚀疲劳表面保护膜。本试验结果已成功地指导了延长内燃机排气阀使用寿命的涂层研究工作。
The hot corrosion-fatigue resistance of three heat-resisting steels, namely: 4CrlOSi2Mo, 18SR, 20-14 and two alloy coatings Co-50, Ni-81 are studied in this paper. For the sake of contrast, the "HCF" ( hot corrosionfatingue test) method was used under an automatic immediate comparative condition with the spraying of NaCl-Na_2SO_4 salt solution. The degree of corrosion failure is measured by depth of corrosion of samples. The hot corrosionfatigue failure process of various steels and the veasons for effective resisting hot corrosion-fatigue of two alloy coatings are investigated by means of metallography, X-ray diffraction and electron probe analysis techniques. In the "HCF" testing condition, it is found that:(1) The loose corrosion products on heat-resisting steels crack and flake away layer after layer. Sulphur and oxygen penetrate immediately into the interior of steels, with oxygen penetrateation deeper than that of sulphur. (2) The degree of hot corrosion-fatigue failure of the heat-resisting steels depends mainly on the type of their internal erosion zone. (3)A compact protective film is formed on the surface of alloy coatings, no matter it is Ni-base or Co-base alloy coatings. This test can be successfully applied to the study of coatings used for extending the service life of internal combustion engine exhaust valves.
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