Research On Erosion And Wear Mechanism Of Corrosion-resistant Alloy For High-pressure And High-output Sand Gas Well Caged Choke Valve

Erosive wear is a common failure type for corbula type throttle valve during natural gas exploitation process,high pressure gas carrying the impurity particles cause erosive wear to the valve core during the process of throttling depressurization,resulting in regulating pressure and production failure of valve,Frequent replacement of valve core can seriously affect the normal production of gas field,reduce gas production efficiency,and increase gas production cost as well.WC-Co cemented carbide is the main material of manufacturing throttle valve core,further study of erosive wear mechanism of WC-Co cemented carbide,not only can provide theoretical guidance to improve erosive wear resistance of valve core and increase its service life,but also remains very important theoretical value and engineering significance.This article focuses on the change rules of erosive wear of WC-Co cemented carbide with several experimental factors,and the erosion and wear mechanism of WC-Co cemented carbide under the impact of gas laden sand particles is analyzed.This article is mainly to carry out the research from the following aspects:(1)A gas jet erosion machine is built as a platform for erosive wear test,and WC-Co cemented carbide erosive wear test scheme is designed based on single factor variable method.Taking the mass erosion wear rate as the wear measurement method,the effects of working condition factors,grinding material properties and target material properties on the erosive wear of 5 different WC-Co cemented carbides(YG3,YG8,YG8C,YG8X and YG15)are studied.Scanning electron microscope and energy spectrum analysis are used to observe the microstructure and element change of the erosive area,in order to summarize the erosive mechanism of WC-Co cemented carbides.(2)There is an obvious "particle size effect" for WC-Co cemented carbides when 3 different sizes(47?m?62?m?125?m)of brown fused aluminas are used as grinding materials in the erosive wear test,under the impatct of brown fused aluminas of which the particle size are within the scope of 47?m?125?m,the erosive wear rate firstly increases with the increasement of size of brown fused aluminas,then decreases after a maximum value is reached,the curve is similar to a parabola.The erosion wear rate caused by brown fused alumina with particle size of 62?m is the highest,followed by 125?m,and the wear rate is the lowest when the particle size is the minimum of 47?m.(3)The effect of hardness of grinding materials on the erosive wear of WC-Co cemented carbide shows that the erosion wear rates of 3 kinds of grinding materials with different hardness and shape are obviously different.The erosive wear rate does not always increase with increasement of hardness of grinding materials,brown fused aluminas of which the hardless is within 19?22Gpa causes highest wear rate;followed by silicon carbide of which the hardless is within 29?31 Gpa,highly crushing property of silicon carbide is the main reason for decreasing erosion damage of target material;glass sand with the lowest hardness caused the minimum wear rate.(4)The influence of working condition factors on the erosive wear of WC-Co cemented carbide is analyzed,the results show that the wear rate of cemented carbide increases with the increasement of erosion angle(30°?90°)and impact velocity,showing a erosive wear characteristics of brittle material.The time of cemented carbide entering the stable wear period is short,the wear mass and time are basically linear after entering stable wear period under the fixed test condition.(5)Microstructure analysis and element analysis results of erosive damage zone show that the removal of binder phase is the main reason for causing erosive wear to the WC-Co cemented carbide,while the erosive angle is low,cutting and ploughing is the main damage morphologys,while the erosive angle is 90°,main damage morphologys are pit and protruding particles caused by WC particles falling off,accompanied with a small amount of cutting and ploughing,extrusion forging fatigue flake and cross crack extension.Reducing Co content and refining WC grain size under guaranteed strength can improve the erosive wear resistance of WC-Co cemented carbide.