*3.4.FractureCharacteristics*

**Table 3.** Elongation and yield strength of the welded joints without and with PWHT.

Figure 9 represents the fracture surface images of the joints without and with PWHT of 730 ◦C. The fracture of the as-welded joint occurred in the weldment; the failed surface contained cleavage fracture characteristics and it is considered to be a mainly brittle fracture. In all cases investigated for PWHT, the weld seam was strengthened and CB2 steel became a weak part, causing fractures that occurred in the CB2 side. The post fracture microstructures of the joints were similar and there were many dimples on the fracture surface. The results indicate that the PWHT process improved the microstructure and mechanical properties of the weldment, thereby avoiding brittle fracture at the weld.

**Figure 9.** Typical fracture surface SEM images of the joints: (**a**) without PWHT and (**b**) with PWHT, at 730 ◦C for 2h.

## **4. Conclusions**

In this paper, the microstructures and mechanical properties of the weldment between G115 and CB2 steels without and with PWHT were studied. The related conclusions can be drawn as follows:


**Author Contributions:** J.X. (Jiankun Xiong), X.Y., J.Y., L.Y., and J.X. (Jian Xu) formulated the original problem, designed the study, developed the methodology, and wrote the manuscript. J.X. (Jiankun Xiong), T.L., X.Y., G.M. and J.X. (Jian Xu) performed the welding, testing, characterization and collected data. J.X. (Jiankun Xiong) and G.M. controlled the materials selection. J.X. (Jiankun Xiong) and X.Y. provided guidance and interpretation of data. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was financially supported by the Sichuan Deyang Open University-City Cooperative Technology Research and Development Project (Project No.: 2018CKJ004) and the Sichuan Deyang Industry-University-Research Cooperation Technology R&D Project (Project No.: 2019CK094). This research was also supported by the fund of Sate Key Laboratory of Long-life High Temperature Materials (Project No.: DTCC28EE190934).

**Conflicts of Interest:** The authors declare no conflict of interest.
