LAUSR

Abstract Thread galling is a common problem when tightening fasteners. In this research, zinc oxide (ZnO) nanofluids are studied as potential thread lubricants with the goal of eliminating or minimizing galling. The agglomeration of nanofluids results in severe wear, higher friction and other antagonistic behaviors. Therefore, it is important to find suitable surfactants to sufficiently disperse and stabilize the nanoparticles. In this study, various ratios of ZnO nanoparticles were mixed with oleic acid (OA) and polyisobutylene succinic anhydride (PIBSA) surfactants in a polyalphaolefin (PAO) base oil. Dynamic light scattering (DLS) was used to measure the size of ZnO nanoparticles mixed with OA/PIBSA before and after tribotests. PIBSA mixed with ZnO nanoparticles produced superior dispersion and stability than OA mixed with ZnO nanoparticles both before and after tests. A ball on disk rotational tribometer was employed to characterize the friction and wear performance of the prepared nanofluids. Generally, the base oil resulted in significant adhesive wear and microploughing. The addition of OA or PIBSA mitigated the adhesive wear and only mild microploughing was found, because of adsorbed monolayers. However, the addition of nanoparticles led to the recurrence of adhesive wear.