Ageing Effects on Room-Temperature Tensile Properties and Fracture Behavior of Quenched and Tempered T92/TP316H Dissimilar Welded Joints with Ni-Based Weld Metal

Abstract

The present work is focused on the investigation of isothermal ageing effects on room-temperature tensile properties and the failure of quenched and tempered martensitic/austenitic weldments between T92 and TP316H heat-resistant steels. The dissimilar weldments were produced by gas tungsten arc welding technique using a Ni-based Thermanit Nicro 82 filler metal. The welded joints were subjected to unconventional post-welding heat treatment consisting of the welds solutionizing (1060 °C/30 min), followed by their water quenching and final stabilization tempering (760 °C/60 min). The treatment was completed by spontaneous air cooling within a tempering furnace. The welds in their initial quenched and tempered condition were subsequently aged at 620 °C for up to 2500 h. Apart from room-temperature tensile tests performed for all the welds material states, additional cross-weld hardness measurements were carried out on longitudinal sections of broken tensile specimens. The applied thermal exposure resulted in recognizable deterioration of plastic properties, whereas their effects on strength properties were rather small. The welds tensile straining and fracture evolution exhibited competitive behavior between the austenitic TP316H region and Ni-based weld metal. The observed failure locations showed significant hardness peaks due to intensive, necking-related strain hardening effects occurred during the tensile tests.

The Effects of Electrochemical Hydrogen Charging on Room-Temperature Tensile Properties of T92/TP316H Dissimilar Weldments in Quenched-and-Tempered and Thermally-Aged Conditions

“…In the present study the same type of T92/TP316H dissimilar weldment was investigated as was also studied in our preceding work [14] about the ageing effects on its room-temperature tensile properties and fracture behavior. The tubes (outer diameter 38 mm, wall thickness 5.6 mm) of T92 tempered martensitic and TP316H austenitic heat-resistant steels were circumferentially welded in the company SES a.s. Tlmače, Slovakia by gas tungsten arc welding (GTAW) technique using "Inconel-type" filler metal Thermanit Nicro 82.…”

“…The tubes (outer diameter 38 mm, wall thickness 5.6 mm) of T92 tempered martensitic and TP316H austenitic heat-resistant steels were circumferentially welded in the company SES a.s. Tlmače, Slovakia by gas tungsten arc welding (GTAW) technique using "Inconel-type" filler metal Thermanit Nicro 82. The details concerning the weld preparation can be found in [14]. Chemical composition of individual base materials and Ni-based filler metal (Thermanit Nicro 82) is shown in Table 1.…”

“…In general, the HAZ region with its strongly heterogeneous microstructure, so-called "HAZ microstructural gradient", is considered to be the critical region of welded joints because of its high propensity for several types of cracking and final failure occurrence [9,10]. The findings of our several former studies about dissimilar T92/TP316H weldments [11][12][13][14] have clearly indicated that the HAZ microstructural heterogeneity can be efficiently suppressed by the application of unconventional "quenching-and-tempering" post-welding heat treatment (QT PWHT). In contrast to microstructural characteristics obtained after conventional "tempering" PWHT (T PWHT), the microstructures of welded base materials after performing QT PWHT became coarser and homogenized with respect to the grain size and state of secondary phase precipitation.…”

“…Our current work represents a direct research continuation of the above described investigation [14]. It is focused on electrochemical hydrogen charging effects on room-temperature mechanical properties of T92/TP316H dissimilar weldments without artificial stress concentrators in "quenched-and-tempered" and thermally-aged conditions.…”

“…Our most recently published study [14] was dealing with isothermal ageing effects on room-temperature tensile properties and fracture behavior of "quenched-and-tempered" T92/TP316H dissimilar weldments with Ni-based weld metal (Ni WM). It has been revealed that the used thermal exposure at 620 • C for up to 2500 h resulted in gradual microstructural changes of individual weld regions.…”