The purpose of this study was to investigate post weld heat treatment (PWHT) of a heat resistant alloy steel used in gas turbines, in terms of microstructural evaluation, carbide phases formation and mechanical properties. EN10302.2002.X10CrMoVNb9-1(DIN1.4903) plates were welded by shielded metal arc welding process using an AWS E9015-B9 electrode, which is a cellulosic coated electrode. PWHTs were conducted at 700 and 740 °C for 4 and 8 h. Optical microscopy, Field Emission Scanning Electron Microscopy (FE-SEM) equipped with Electron Diffraction Spectroscopy (EDS), and X-Ray Diffraction (XRD) analyses were used to study the microstructure of the samples and to perform a thorough analysis. Uniaxial tensile tests, Charpy impact tests and Vickers microhardness were used to assess the mechanical properties of the welded joints. To define the fracture mode, the surfaces of the fractured samples were analyzed by FESEM after tensile and Charpy impact tests. XRD results showed that, in the weld metal, the ferrite phase is formed together with the iron and chromium carbides in the post weld heat treated cases. Whereas mostly martensite is formed in the as-welded condition. It was observed that increasing the PWHT soaking time and temperature increased the amount of ferrite. Results of microstructural observations and phase analyses showed that the microstructure of the weld joints contain ferrite phase together with retained austenite and chromium carbides, as well as niobium carbides. With increasing the temperature and soaking time of the PWHT, the amount of ferrite was increased at the expense of martensite. Assessing the tensile tests and Charpy tests results showed that performing the PWHT decreased yield strength and increased elongation to fracture in the joints. Ductility increased from 10.5% in as-welded condition, to 15% after PWHT at 740 °C for 8h. As such, the yield strength decreased from 600 MPa to 540 MPa after this PWHT process. On the other hand, toughness was improved with increasing the temperature and soaking time of the heat treatment. As well, performing heat treatment removed hardness gradient in these welded joints. Finally, fracture mode analyses by FESEM showed that by performing this specific PWHT process, the fracture mode has changed from brittle to ductile one making it an attractive procedure to pursue industrially.

这项研究的目的是研究燃气轮机中使用的耐热合金钢的焊后热处理（PWHT），包括显微组织评估，碳化物相形成和机械性能。EN10302.2002.X10CrMoVNb9-1（DIN1.4903）板使用AWS E9015-B9焊条通过屏蔽金属电弧焊工艺焊接，该焊条是纤维素涂层的焊条。PWHT在700和740°C进行了4和8 h。使用光学显微镜，配备有电子衍射光谱（EDS）的场发射扫描电子显微镜（FE-SEM）和X射线衍射（XRD）分析来研究样品的微观结构并进行彻底的分析。单轴拉伸试验，夏比冲击试验和维氏显微硬度用于评估焊接接头的机械性能。为了确定断裂方式，在拉伸和夏比冲击试验之后，通过FESEM分析断裂样品的表面。XRD结果表明，在焊缝热处理后的焊接金属中，铁素体相与碳化铁和碳化铬一起形成。而大多数马氏体是在焊接状态下形成的。观察到增加PWHT均热时间和温度会增加铁素体的数量。显微组织观察和相分析的结果表明，焊接接头的显微组织包含铁素体相，残留的奥氏体和碳化铬以及碳化铌。随着PWHT的温度和保温时间的增加，铁素体的数量增加了，但以马氏体为代价。评估拉伸试验和夏比试验结果表明，进行PWHT会降低接头的屈服强度并增加断裂伸长率。延展性从焊接时的10.5％上升到740°C进行8小时的PWHT后的15％。这样，在该PWHT工艺之后，屈服强度从600MPa降低至540MPa。另一方面，随着热处理的温度和均热时间的增加，韧性提高。同样，进行热处理消除了这些焊接接头的硬度梯度。最后，通过FESEM进行的断裂模式分析表明，通过执行这一特定的PWHT工艺，断裂模式已从脆性转变为延性，使其成为工业上有吸引力的程序。延展性从焊接时的10.5％上升到740°C进行8小时的PWHT后的15％。这样，在该PWHT工艺之后，屈服强度从600MPa降低至540MPa。另一方面，随着热处理的温度和均热时间的增加，韧性提高。同样，进行热处理消除了这些焊接接头的硬度梯度。最后，通过FESEM进行的断裂模式分析表明，通过执行这一特定的PWHT工艺，断裂模式已从脆性转变为延性，使其成为工业上有吸引力的程序。延展性从焊接时的10.5％上升到740°C进行8小时的PWHT后的15％。这样，在该PWHT工艺之后，屈服强度从600MPa降低至540MPa。另一方面，韧性随着热处理温度和保温时间的增加而提高。同样，进行热处理消除了这些焊接接头的硬度梯度。最后，通过FESEM进行的断裂模式分析表明，通过执行这一特定的PWHT工艺，断裂模式已从脆性转变为韧性，使其成为工业上有吸引力的程序。韧性随着热处理温度和保温时间的增加而提高。同样，执行热处理消除了这些焊接接头的硬度梯度。最后，通过FESEM进行的断裂模式分析表明，通过执行这一特定的PWHT工艺，断裂模式已从脆性转变为韧性，使其成为工业上有吸引力的程序。韧性随着热处理温度和保温时间的增加而提高。同样，进行热处理消除了这些焊接接头的硬度梯度。最后，通过FESEM进行的断裂模式分析表明，通过执行这一特定的PWHT工艺，断裂模式已从脆性转变为韧性，使其成为工业上有吸引力的程序。