1971 Volume 57 Issue 2 Pages 355-366
An extensive study has been made on corrosion characteristics and mechanical properties of S590 alloy chromized by powder method. Chromized S590 alloy showed slight gradual weight gain and was not suffered from accelerated corrosion when it was exposed in combustion gas of buncker C residual fuel at a velocity of 40-50 m/sec and at a temperature of 720-790°C for 600 hr, while the same alloy without chromized layer indicated a remarkable weight loss according to linear rate law.
Chromizing was also proved to be very effective by full immersion test and contact test using synthetic fuel ash. There were some changes in corrosion resistance of chromized S590 in synthetic fuel ash depending on chromizing method by Cr-Al2O3 powder mixture and that by Cr-Fe-Al2O3 mixture due to differences of surface chromium concentration of the layer.
When solution treated and aged S590 alloy was chromized at 1050°C for 10 hr, some deterioration of mechanical properties were observed. This deterioration resulted from resolutionof fine carbides and coagulation of coarse carbides.
Among various heat treatments prior and posterior to chromizing, the following process was proved to be most favourable for mechanical properties of chromized S590, that is, solution treatment at 1180°C→chromizing at 1050°C for 10 hr, →aging at 760°C for 16 hr.
