Repulsive Interaction Of Sulfide Layers On Compressor Impeller Blades For Thermal Spray Welding And Thermal Spraying

Centrifugal compressors are widely used in long-distance oil and gas transmission in West-to-East natural gas transmission project.The blade is a key component of centrifugal compressor and it rotates at high speed to work on gas in the pipeline under the action of the drive shaft.Remanufacturing engineering is the best form and preferred way for discarded centrifugal compressor blades and can make most use of their inherent values.Long pipeline centrifugal compressors are often scrapped due to the corrosion failure of their blades;and sulfide layers formed by corrosion have strong repulsive interaction to the subsequent remanufacturing process.To describe its mechanism and provide options for remanufacturing process,two kinds of remanufacturing process,including thermal spray welding and thermal spraying were selected to further research that repulsive interaction of sulfide layers on compressor impeller blades for remanufacturing in this paper.The main work of this paper is as follows:The mechanism of corrosion on the surface of the blade was simulated;and the sulfide layer was prepared in the laboratory.The microstructure,elements content and elements distribution of sulfide layers were conducted through scanning electron microscope(SEM)and energy disperse spectroscopy(EDS).Phase analysis of double-layered sulfides was analyzed by X-ray diffraction(XRD);and results showed that double-layered sulfides were composed of Cr3S4,Cr2S3/Fe7S8,and Ni Cr2S4 from the outside to the inside.Meanwhile surface topography analysis of sulfide layers was detected by three dimensional profilometer.After these studies,the corrosion law of the blades in the H2 S environment was determined.For the main failure reason of blades is H2 S corrosion,the plasma spray welding(PSW)and high velocity oxy-fuel(HVOF)spraying were used to study repulsive interaction of sulfide layers on compressor impeller blades for thermal spray welding and thermal spraying,respectively.The paper introduced the test principles and methods for PSW.The microstructure of cladding layer was analyzed by metallographic examination;the hardness analysis of metal matrix and sulfide inclusions was detected through hardness test;the mechanical properties of samples were analyzed by tensile test;and the failure reason oftensile samples was evaluated by fracture surface analysis.The paper also introduced the experimental methods for remanufacturing samples using HVOF.The microstructure and elements distribution of coating were observed and analyzed by SEM and EDS,respectively;and the bonding strength between coating and substrate was measured by scratch test.The results of blade remanufacturing test show that remanufacturing samples covered by sulfide layers cannot obtain good performance by PSW or HVOF,and that the suitable cleaning process should be selected to remove the sulfide layers on compressor impeller blades in the remanufacturing process.