Research on Corrosion Resistance of 316L/X65 Composite Lined Pipe End
The microstructure analysis,composition analysis,intercrystal corrosion and point corrosion tests were conducted on 316L/X65 composite lined pipe end for oil and gas pipeline.The results show that the chemical composition of the composite pipe is qualified.The performance indicators are all qualified.The welding layer is divided into two layers,the microstructure of the weld zone is mainly austenite and the crystalline grain of outer layer is smaller than that of the inner layer.Due to the barrier of the inner layer,the outer layer is not effected by X65 substrate,which ensures good corrosion resistance.Pitting corrosion resistance from low to high order is 316L-Inconel625 weld zone<316L liner<Inconel625 welded layer,increasing temperature significantly reduces the point corrosion resistance of the pipe end.Because of electric coupling,the welded joint between the 316L lined pipe and Inconel625 pile welding layer makes 316L be prone to corrosion.
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