Effects of direct current field on powder pack aluminising

Direct current field (DCF) has been applied on an aluminising specimen and powder aluminising agents to overcome conventional powder pack aluminising (CPA)’s shortcomings of high treating temperature, long soaking time and low efficiency in utilising aluminising media. The specimen in the shape of plate or tube was taken as cathode of the DCF. The anode in the shape of plate or column paralleled to the specimen. Effects of DCF on CPA have been studied. The treated case’s microstructure, phase, thickness and oxidation resistance have been investigated. The results show that DCF has the function of enhancing aluminising with great energy saving, even at a temperature below 750°C. The aluminised case endows plain carbon steel with superior resistance to oxidisation in air at a high temperature of 850°C. Mechanisms of DCF’s effects to CPA have been proposed, which were discussed from two aspects of the DCF’s thermal and non‐thermal effects to the aluminising process.