Influence factors and evaluation system of steam treatment film on iron-based powder metallurgy parts

Steam treatment (ST) is a widely used chemical strengthening method for the iron-based powder metallurgy (PM) products, which can form the dense protective films with strong adhesion force and high hardness on the product surface, showing the effects of corrosion resistance, wear resistance, and hardness enhancement. The reaction principle of steam treatment and the influence of reaction thermodynamics and dynamics on the quality of the steam treated protective films were described systematically in this paper. To promote the standardization of steam treatment process for the iron-based powder metallurgy parts, the detection methods of thickness, structure, composition, and binding force of the steam treatment protective films were summarized, based on the current production situation; and combined with the actual experimental results, the advantages and disadvantages for each detection method were explained.