Effect of Overheating Temperature on Microstructure and Hardness of HP40 Nb Alloy: Analysis by ANOVA

In this study, the influence of short-term overheating on the microstructure and hardness of tube segments made of centrifugally cast austenitic alloy HP40 Nb that were exposed to high temperatures in a stream of hydrocarbons and water vapor, at low pressure for more than 100,000 hours has been studied. Samples were heated up to 1223, 1323, and 1423 K under air at different time intervals from 30 to 480 min, respectively. Microstructural investigation and chemical analysis of as-cast and heat-treated specimens were performed by scanning electron microscopy and energy dispersive spectroscopy. The results showed significant differences in microstructure and hardness after short-term overheating. The results obtained were analyzed using regression analysis and ANOVA methods. The highest hardness of 203.85 HV10 was obtained after overheating at 1223 K for 480 min. The test results were analyzed using regression analysis and ANOVA test. ANOVA test confirmed the results with a 71.82 % model representativeness for hardness. This paper provides insights into the effects of short-term overheating on the mechanical properties of HP40 Nb grade steel after long-term operating conditions at high temperatures, which may be significant for improving performance and predicting the remaining life of the tubes made of HP40 Nb.