Effect of deep cryogenic treatment on C93700 bearing bush material used in submersible pumps

Abstract

Bearing bush is an essential part of a rotating machine. It is inserted in a housing to support the motor shaft of a submersible pump with a radial clearance of 40 μm. This plain bearing is made of high lead tin Bronze, C93700. In the working condition the submersible pump stacked with series of impellers is assumed to be an overhanging structure as the fluid flow through the impellers is not uniform in the beginning. This imbalance leads to the misalignment between pump and motor shafts resulting in the contact of bearing bush with motor shaft, as the shaft material AISI 420 stainless steel is harder than the bearing material, wear out of latter is inevitable. Due to the continuous running of motor in this condition for long hours, the shaft comes in contact with the stator and the stator coils begin to burn implying the breakdown of pump set within 6–12 months of installation. This paper aims to improve the hardness and wear resistance of C93700 bronze through deep cryogenic treatment. The test samples of the material were treated with liquid Nitrogen at −196℃ temperature and tested for tensile strength, hardness and wear resistance. Microstructure of the samples have been examined using SEM and chemical analysis was done through EDS.