Speaker
Description
Corrosion resistance may be of some importance if the tools are operated in harsh environments that contain acids, seawater or other chemical substances. Therefore it is appropriate to control this property carefully, by using proper heat treatment route. One of possible ways how to change the corrosion resistance of tool steels is the application of cryogenic treatment. This treatment reduces the retained austenite amount, produces extra carbides in steels microstructures, changes the precipitation of nano-sized carbides, and makes an overall microstructural refinement. These microstructural alteration change the corrosion potentials of exposed surfaces, and thereby the materials resistance against corrosion. In this paper the impact of cryogenic treatments on corrosion resistance is demonstrated upon an example of Vanadis 6 steel. This steel was subjected to different combinations of cryogenic treatments (-75, 140, -196 or -269°C) and tempering (no, 170, 330, 450 or 530°C). Then, the steel specimens were tested by potentiodynamic polarization method, in 3.5% NaCl solution. A general improvement of corrosion resistance of the material was recorded due to cryogenic treatment, with the maximum improvement after cryogenic treatment at -140°C. It was suggested that enhanced number and more uniform distribution of carbides can more than sufficiently compensate lowered retained austenite amounts, thus induce improved corrosion resistance.
Speaker Country | Slovakia |
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