Complex tribology of bolted assembly

Threaded fasteners are widely used in various popular areas such as mechanical, civil, transport, medical, space, and many more because of extreme assembly and disassembly facilities. An everyday activity during the use of bolts is their reuse. In this work, inorganic and organic topcoats were used as a lubricant to investigate their influence on tribological properties. Grease-based lubrication was used after the three-time cyclic tightening to find the performance when it was reused. The tightening process was divided into two steps: from the specific torque value to the yield point. The clamping force and the surface morphology was monitored and analysed during cyclic tightening. Experimental results showed that the use of lubrication was able to increase the clamping force of the threaded fasteners. With an inorganic topcoat, obtained clamping force during cyclic tightening was more stable than that using organic topcoat. Even through significant friction and wear were observed during cyclic tightening, the higher clamping force can also be kept with additional lubricant when threaded fasteners were reused. The results helped to provide insight into the influence of surface treatment on the tribological behaviour of threaded fasteners during cyclic tightening.