High load capability, sticking scale inhabitation and promising lubrication of sodium carbonate coating for steel/steel contact at high temperature

Adequate lubrication for the sliding contacts is responsible for the energy saving and long service life. In this work, load-dependence of tribological behaviours of sodium carbonate coating on the stainless steel was evaluated by ball-on-disc friction test at high temperatures. The results suggested that this sodium carbonate coating showed promising lubrication even under high applied load of 1800 N (Hertz pressure is 6.14 GPa). Apart from the improvement of lubricity, it can also inhibit adhesive wear that transfer oxide scale from the disc to the ball under dry sliding condition. The desirable lubrication and load-carrying capability were attributed to the frictional heat induced in-situ formed sodium carbonate melt that produced an easily sheared tribo-interface, as well as the reconstruction of the oxide scale. The sodium carbonate coating with a superior load capability at high temperature is initially reported here. This finding is believed to bring new perspective of high-temperature, extreme-pressure lubrication design with the easily accessible carbonate salt.