The Effects of Various Conditions of Short-Term Rejuvenation Heat Treatment on Room-Temperature Mechanical Properties of Thermally Aged P92 Boiler Steel
In this work, the effects of various conditions of short-term rejuvenation heat treatment on room-temperature mechanical properties of long-term aged P92 boiler steel were investigated. Normalized and tempered P92 steel pipe was thermally exposed at 600 °C for time durations up to 5000 h in order to...
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2021-10-01
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| Online Access: | https://www.mdpi.com/1996-1944/14/20/6076 |
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| author | Ladislav Falat Lucia Čiripová Viera Homolová Miroslav Džupon Róbert Džunda Karol Kovaľ |
| author_facet | Ladislav Falat Lucia Čiripová Viera Homolová Miroslav Džupon Róbert Džunda Karol Kovaľ |
| author_sort | Ladislav Falat |
| collection | DOAJ |
| description | In this work, the effects of various conditions of short-term rejuvenation heat treatment on room-temperature mechanical properties of long-term aged P92 boiler steel were investigated. Normalized and tempered P92 steel pipe was thermally exposed at 600 °C for time durations up to 5000 h in order to simulate high-temperature material degradation, as also occurring in service conditions. Thus, thermally embrittled material states of P92 steel were prepared, showing tempered martensitic microstructures with coarsened secondary phase precipitates of Cr<sub>23</sub>C<sub>6</sub>-based carbides and Fe<sub>2</sub>W-based Laves phase. Compared with the initial normalized and tempered material condition, thermally aged materials exhibited a slight decrease in strength properties (i.e., yield stress and ultimate tensile strength) and deformation properties (i.e., total elongation and reduction of area). The hardness values were almost unaffected, whereas the impact toughness values showed a steep decrease after long-term ageing. An idea for designing the rejuvenation heat treatments for restoration of impact toughness was based on tuning the material properties by short-term annealing effects at various selected temperatures somewhat above the long-term ageing temperature of P92 material. Specifically, the proposed heat treatments were performed within the temperature range between 680 °C and 740 °C, employing variable heating up and cooling down conditions. It was revealed that short-term annealing at 740 °C for 1 h with subsequent rapid cooling into water represents the most efficient rejuvenation heat treatment procedure of thermally aged P92 steel for full restoration of impact toughness up to original values of normalized and tempered material state. Microstructural observations clearly indicated partial dissolution of the Laves phase precipitates to be the crucial phenomenon that played a key role in restoring the impact toughness. |
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| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-10T06:26:09Z |
| publishDate | 2021-10-01 |
| publisher | MDPI AG |
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| series | Materials |
| spelling | doaj.art-97b75572146c48e39ec4bf43ea4e65eb2023-11-22T18:58:34ZengMDPI AGMaterials1996-19442021-10-011420607610.3390/ma14206076The Effects of Various Conditions of Short-Term Rejuvenation Heat Treatment on Room-Temperature Mechanical Properties of Thermally Aged P92 Boiler SteelLadislav Falat0Lucia Čiripová1Viera Homolová2Miroslav Džupon3Róbert Džunda4Karol Kovaľ5Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 04001 Košice, SlovakiaInstitute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 04001 Košice, SlovakiaInstitute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 04001 Košice, SlovakiaInstitute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 04001 Košice, SlovakiaInstitute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 04001 Košice, SlovakiaInstitute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 04001 Košice, SlovakiaIn this work, the effects of various conditions of short-term rejuvenation heat treatment on room-temperature mechanical properties of long-term aged P92 boiler steel were investigated. Normalized and tempered P92 steel pipe was thermally exposed at 600 °C for time durations up to 5000 h in order to simulate high-temperature material degradation, as also occurring in service conditions. Thus, thermally embrittled material states of P92 steel were prepared, showing tempered martensitic microstructures with coarsened secondary phase precipitates of Cr<sub>23</sub>C<sub>6</sub>-based carbides and Fe<sub>2</sub>W-based Laves phase. Compared with the initial normalized and tempered material condition, thermally aged materials exhibited a slight decrease in strength properties (i.e., yield stress and ultimate tensile strength) and deformation properties (i.e., total elongation and reduction of area). The hardness values were almost unaffected, whereas the impact toughness values showed a steep decrease after long-term ageing. An idea for designing the rejuvenation heat treatments for restoration of impact toughness was based on tuning the material properties by short-term annealing effects at various selected temperatures somewhat above the long-term ageing temperature of P92 material. Specifically, the proposed heat treatments were performed within the temperature range between 680 °C and 740 °C, employing variable heating up and cooling down conditions. It was revealed that short-term annealing at 740 °C for 1 h with subsequent rapid cooling into water represents the most efficient rejuvenation heat treatment procedure of thermally aged P92 steel for full restoration of impact toughness up to original values of normalized and tempered material state. Microstructural observations clearly indicated partial dissolution of the Laves phase precipitates to be the crucial phenomenon that played a key role in restoring the impact toughness.https://www.mdpi.com/1996-1944/14/20/6076thermal embrittlementLaves phaserejuvenation heat treatmentimpact toughnessstatic tensile properties |
| spellingShingle | Ladislav Falat Lucia Čiripová Viera Homolová Miroslav Džupon Róbert Džunda Karol Kovaľ The Effects of Various Conditions of Short-Term Rejuvenation Heat Treatment on Room-Temperature Mechanical Properties of Thermally Aged P92 Boiler Steel Materials thermal embrittlement Laves phase rejuvenation heat treatment impact toughness static tensile properties |
| title | The Effects of Various Conditions of Short-Term Rejuvenation Heat Treatment on Room-Temperature Mechanical Properties of Thermally Aged P92 Boiler Steel |
| title_full | The Effects of Various Conditions of Short-Term Rejuvenation Heat Treatment on Room-Temperature Mechanical Properties of Thermally Aged P92 Boiler Steel |
| title_fullStr | The Effects of Various Conditions of Short-Term Rejuvenation Heat Treatment on Room-Temperature Mechanical Properties of Thermally Aged P92 Boiler Steel |
| title_full_unstemmed | The Effects of Various Conditions of Short-Term Rejuvenation Heat Treatment on Room-Temperature Mechanical Properties of Thermally Aged P92 Boiler Steel |
| title_short | The Effects of Various Conditions of Short-Term Rejuvenation Heat Treatment on Room-Temperature Mechanical Properties of Thermally Aged P92 Boiler Steel |
| title_sort | effects of various conditions of short term rejuvenation heat treatment on room temperature mechanical properties of thermally aged p92 boiler steel |
| topic | thermal embrittlement Laves phase rejuvenation heat treatment impact toughness static tensile properties |
| url | https://www.mdpi.com/1996-1944/14/20/6076 |
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