CREEP PROPERTIES OF T92/HR3C WELDED JOINTS 89 o「 Fig. 7 Macroscopic morphologies of ruptured welded joints under different load stresses(a)180, (b)130, (c)110 MPa. 19 000 h) and P91/P91 similar steels welded joint (less Figure 8 presents the micromorphologies of cross- than 32 000 h). 26 Relevant data of T92 welded joints have section of the ruptured sample under 180 MPa. It can be seen from Fig. 8a that the diameter of the cross-section is about 2.5 mm. Compared with its original value of 6.0 mm, the reduction in area y can be calculated as about fractograph observation of creep ruptured samples 80%. As is shown in Fig. 8. the cross-section is covered with densely distributed spherical creep voids, whose di According to the creep rupture test results, the rupture ameter ranges from 5 to 50 um. The presence of creep positions of the T92/HR3C dissimilar steels welded joints voids, whose nucleation mechanisms still need to be fur under different load stresses, mainly including three dif- ther identified lonly represents a good toughness ferent parts, seen in Table 5. Hence, fractograph of sam- of materials at high temperatures. In some region,three ples under three representative load stresses: 110, 130 and neighbouring voids with diameters of about 5 um have 0 Mpa, whose rupture positions were respectively weld coalesced into a larger wave-like one, whose axial width seam,HAZ of T92 and T92 base material, were then has already reached nearly 20 um, as can be seen in Fig.8c concretely inspected by means of SEM. Fracture posi- and d. This is typical evidence for ductile materials that tions of joints under 110, 130 30 MPa located in creep rupture is led by the coalescence of microscopic three different positions. Figure 7 was the macroscopic cracks which are also generated by the sub-coalescence of morphology of them three. Then, samples were cut from creep voids the rupture positions to observe the micromorphologies Compared with the fractograph of ruptured sample un- of their cross-sections under sem der 180 MPa, the fractograph under 130 MPa displays @2010 Blackwell Publishing Ltd Fatigue Fract Engng Mater Struct 34, 83-96C R E E P P RO P E RTI E S O F T 9 2/H R 3 C W E LD ED JOINT S 89 Fig. 7 Macroscopic morphologies of ruptured welded joints under different load stresses (a) 180, (b) 130, (c) 110 MPa. 19 000 h) and P91/P91 similar steels welded joint (less than 32 000 h).26 Relevant data of T92 welded joints have hardly been found. Fractograph observation of creep ruptured samples According to the creep rupture test results, the rupture positions of the T92/HR3C dissimilar steels welded joints under different load stresses, mainly including three dif￾ferent parts, seen in Table 5. Hence, fractograph of sam￾ples under three representative load stresses: 110, 130 and 180 Mpa, whose rupture positions were respectively weld seam, HAZ of T92 and T92 base material, were then concretely inspected by means of SEM. Fracture posi￾tions of joints under 110, 130 and 180 MPa located in three different positions. Figure 7 was the macroscopic morphology of them three. Then, samples were cut from the rupture positions to observe the micromorphologies of their cross-sections under SEM. Figure 8 presents the micromorphologies of cross￾section of the ruptured sample under 180 MPa. It can be seen from Fig. 8a that the diameter of the cross-section is about 2.5 mm. Compared with its original value of 6.0 mm, the reduction in area ψ can be calculated as about 80%. As is shown in Fig. 8b, the cross-section is covered with densely distributed spherical creep voids, whose di￾ameter ranges from 5 to 50 μm. The presence of creep voids, whose nucleation mechanisms still need to be fur￾ther identified, commonly represents a good toughness of materials at high temperatures. In some region, three neighbouring voids with diameters of about 5 μm have coalesced into a larger wave-like one, whose axial width has already reached nearly 20 μm, as can be seen in Fig. 8c and d. This is typical evidence for ductile materials that creep rupture is led by the coalescence of microscopic cracks which are also generated by the sub-coalescence of creep voids. Compared with the fractograph of ruptured sample un￾der 180 MPa, the fractograph under 130 MPa displays c 2010 Blackwell Publishing Ltd. Fatigue Fract Engng Mater Struct 34, 83–96