Research On Aluminized Layer Phase Of Gathering Pipeline Steel

In order to improve the corrosion resistance of16Mn gathering pipeline steel by packaluminizing and maintain its good natural mechanical properties, a rapid low-temperature packaluminizing process under560。C was carried out on16Mn gathering pipeline steel withself-nanocrystal1ization surface fulfilled by surface mechanical attrition treatment (SMAT),Remove the aluminizing source and give the aluminized sample heat treatment of the differentprocesses after the aluminizing process completed.The phase composition and micro structure ofas-prepared aluminizing layer were characterized by means of scanning electron microscope(SEM)’ energy dispersive spectroscopy (EDS) respectively. Based on the data we can find theinfluence of different factors on the phase formation of aluminized layer. Moreover, thecorrosion resistance and failure mechanism of16Mn gathering pipeline steel with aluminizinglayer were also analyzed. Some main conclusions are listed as follows:A dense aluminizing layer with uniform thickness can be obtained under530°C onlypacking for2hours on the surface of16Mn gathering pipelines steels pre-treated by SMAT atdifferent pack powder.16Mn gathering pipeline steel with self-nanocrystallization surface not only own the higheraluminized speed higher but also get thick aluminizing layer which rich in low aluminum phase.When the pack powder become liquid state, the effects of SMAT processing will be moreobvious, that mean the surface with nano structure to spread out on the surface of the liquid onpermeability and wettability have obvious promoting effect Zn can low the melting points of thepack powder which lead to an enough spreading and wetting during the pack aluminizingprocessing, so as to promote the aluminizing, resulting in thicker and with low aluminum phaselayer. After rare earth atoms into the sample surface and formation aluminizing layer, can greatlyreduce the void in the aluminizing layer and make more dense and rich in low aluminum phaselayer.After heat treatment, the aluminizing atomic layer can diffuse from high concentration tolow concentration, while the high aluminum layer in the phase of decomposition reactiongenerating low aluminium. The function of the heat treatment will increase with the heattreatment temperature and holding time prolonged and the performance is more obvious. Under the simulation corrosion environment of real service condition of pipeline steel, the16Mn gatheirng pipeline steel exhibits a better general and pitting corrosion resistance. Inaddition, the erosion corrosion resistance of16Mn pipeline can also be improved by the packaluminizing.