Creep Behavior and Life Assessment of a Novel Heat-Resistant Austenite Steel and Its Weldment

Abstract

In the present study, creep activation energy for rupture was obtained as 221-348 kJ/mol for 22Cr15Ni3.5CuNbN due to the precipitation-hardening mechanism. The extrapolation strength of creep rupture time of 10 5 h at 923 K for 22Cr15Ni3.5CuNbN is more valid (83.71 MPa) predicted by the Manson-Haferd method, which is superior to other commercial heat-resistant steels. The tensile creep tests ranging from 180 to 240 MPa at 923 K were conducted to investigate creep deformation behavior of welded joint between a novel heat-resistant austenite steel 22Cr15Ni3.5CuNbN and ERNiCrCoMo-1 weld metal. Apparent stress exponent value of 6.54 was obtained, which indicated that the ratecontrolled creep occurred in weldment during creep. A damage tolerance factor of 6.4 in the weldment illustrates that the microstructural degradation is the dominant creep damaging mechanism in the alloy. Meanwhile, the welded joints perform two types of deformation behavior with the variation in applied stress, which resulted from the different parts that govern the creep processing. Also, the morphology evolution of the fracture surfaces confirms the effects of stress level and stress state. Keywords Heat-resistant steel weldment Á Creep deformation Á Life assessment Á TTP (time-temperature parametric) method Recent researches on life assessment of high-temperature alloys used in power plants, nevertheless, mainly converge on grades 91 and 92 [9-13]. The long-term lifetime extrapolation and allowable stress calculation are particularly inadequate for newly developed high-temperature steel. Meanwhile, welding is an inevitable processing

Creep Rupture Behavior in Dissimilar Weldment between FB2 and 30Cr1Mo1V Heat-Resistant Steel

“…Therefore, the weld fusion zone changes from the maximum hardness region to the minimum during creep testing, which is more obvious for the regions on the side near the fusion boundary, indicating that a softening phenomenon occurs in weld metal. This result is different from the results from previous researches on other heat-resistant steel weldments [25,[28][29][30], where hardness of the FGHAZ/IC-HAZ is the lowest, and soft FGHAZ/IC-HAZ shows higher susceptibility to type IV cracking.…”

“…The fitted creep rupture exponent is 14.53, with a coefficient of determination, R 2 , of 0.93477. Zhang et al [25] have successfully utilized this law to predict the creep life of weldments between an austenite heat-resistant steel and a nickel base weld metal at a specified temperature. The extrapolating strength of rupture time at 10,000 h at 783 K (510 °C) can be obtained as 261.67 MPa, which agrees with our experimental data (see Figure 2).…”

Study on Creep Damage of Ni-Based Superalloy Caused by Variable Load Conditions at Elevated Temperatures

“…In general, when creep proceeds, the rupture time exhibits a nonlinear relationship with stress. Norton proposed the relationship between rupture time and stress in the form of an exponential function of stress as follows [22][23][24]:…”

Oxidation Performance and Interdiffusion Behavior of a Pt-Modified Aluminide Coating with Pre-deposition of Ni

“…The original γ/γ′-microstructures in SC substrate are destroyed due to absorption of Al and loss of Ni, where a series of phase transformations occur, forming TCP rods and β-matrix in the IDZ [37]. It is well known that β-phase possesses much lower solubility for refractory elements, such as Cr, W, Mo and Re, than γ-phase [38][39][40]. When γ/γ′ transforms to β-phase, the refractory elements will precipitate out and segregate as particles or rods.…”