Steam treatment is a thermal process that creates a thin controlled oxide layer on the surface of an iron-based metal component. Steam treatment can provide a component with increased corrosion resistance, hardness, density, and magnetic properties. It can also be used to seal the porosity and improve its wear characteristic.
Steam treatment is a batch process with minimal inputs and has been proven to be a cost-effective solution for many applications. Components transferred to steam treat must be kept clean and dry as it is necessary to avoid contaminants or residue on or in the structure prior to processing because it will impact of how well the oxide layer forms on the surface.
As in most thermal treatments, time, temperature and atmosphere are controlled to provide the optimal conditions for the expected finish. The desired properties of the component will dictate what time and process parameters are used for a given part. During a typical steam treatment process, parts are placed in a steam treat unit and heated to approximately 1000° F. Once the component is at temperature, steam is introduced and the water vapor reacts with the iron to form the oxide layer (magnetite - Fe3O4). After a designated period of time, the component is removed from the unit and allowed to cool. The oxide appears on the component surface as a blue/black finish.