Reduced Friction and Excellent Anti-Wear Performance of QBe2 Beryllium Bronze against 38CrMoAlA Steel in Pneumatic Downhole Motor under Grease Lubrication

To improve the service life of the newly designed pneumatic downhole motor, a kind of commercially available lithium complex grease was used to help avoid the rapid wear-induced failure of the dynamic seal of pneumatic downhole tools in operation. The investigation on the tribological behaviors of QBe2 beryllium bronze and 38CrMoAlA steel tribo-pairs in pneumatic downhole motor revealed that under lubrication, the instantaneous friction coefficient and wear volume became very low, showing greatly reduced friction and excellent anti-wear performance. Compared with the case without lubrication, the adhesive wear mechanism and ploughing effect of the tribo-pairs were significantly alleviated. Moreover, Cu and Fe were oxidized to form composite oxides between the frictional surface, further improving the lubrication effect between the QBe2 beryllium bronze and 38CrMoAlA steel. Notably, the test could be operated stably for more than 150 h under lubrication, fully reaching the requirement of pneumatic downhole tools under actual drilling conditions. These results provide a solid support for the practical application of the reported pneumatic downhole tools.

Automated summary

In order to improve the service life of the newly designed pneumatic downhole motor, commercially available lithium complex grease was used to prevent rapid wear-induced failure of the dynamic seal in operation. The investigation on the tribological behaviors of QBe2 beryllium bronze and 38CrMoAlA steel tribo-pairs revealed that lubrication significantly reduced friction and wear volume. Moreover, the oxidation of Cu and Fe formed composite oxides between the frictional surface, further improving the lubrication effect. Stable operation for over 150 hours under lubrication fully met the requirements of pneumatic downhole tools in actual drilling conditions, providing solid support for practical application.