采油螺杆泵定子橡胶的磨粒侵蚀磨损机理

Abrasive-erosive wear mechanism for stator rubber of oil extraction progressing cavity pump

为了揭示橡胶磨粒侵蚀磨损机理,采用MPV-600型磨粒磨损试验机考察了丁腈橡胶(NBR)与转子45#钢配副在不同砂粒浓度原油条件下的磨粒侵蚀磨损行为,并用扫描电子显微镜及x-射线能量散射分析(SEM-EDXA)法对橡胶的磨痕表面形貌、元素成分进行了分析.分析结果表明:NBR摩擦系数随着原油介质中砂粒浓度的增大而增大,但当砂粒浓度增加到一定程度后,其摩擦系数反而减小.NBR磨粒侵蚀磨损的机理是:橡胶表层产生微切削作用而使其发生微观撕裂和变形,由氧化降解形成的胶粘层在磨损过程中不断地形成和被磨损;NBR在含砂原油介质中可能发生了分子链断裂,生成了初级活性自由基,断裂后生成分散性的小分子单体,继而发生异构化.

To reveal the abrasive-erosive wear mechanism of rubber,the abrasive-erosive wear behavior of nitrile butadiene rubber(NBR) and rotor 45#steel pair under the crude oil condition with different sand grain content was investigated with a MPV-600 micro-computer-controlled grain-abrasion testing machine.In addition,the surface wear scar morphology and element constituent of rubber were characterized with scanning electron microscope and energy dispersive x-ray analysis(SEM-EDXA) technique.The results show that with increasing the sand content in the crude oil medium,the friction coefficient of NBR increases.However,the friction coefficient decreases when the sand content increases to a certain extent.The abrasive-erosive wear mechanism of NBR is that the micro-cutting action generated on the rubber surface can cause the microscopic tearing and deformation,and the adhesive layer formed by the oxidative degradation is continuously generated and worn in the wear process.Moreover,the molecular chain rupture of NBR may occur in the sand-containing crude oil medium,the primary reactive free radicals are generated,the small dispersive molecule monomers form after the fracture,and thus the subsequent isomerization occurs.