Creep Behaviour of a Zr-1 wt% Nb Alloy at Elevated Temperatures

Abstract

This paper presents experimental data regarding creep behaviour of a Zr1 wt% Nb alloy at elevated (623 K) and at high temperatures (8731123 K) corresponding to loss-of-cooling situation of fuel cladding tubes for nuclear reactors. For an elaboration of methodological procedure and comparison purposes, the tensile creep tests were conducted using both constant stress and constant load over a wide range of applied stress. The substantial dierences in the acquired creep data between constant stress and constant load creep testing were found especially at high stresses and large creep strain levels.

High-Temperature Creep Tests of Two Creep-Resistant Materials at Constant Stress and Constant Load

“…For given testing temperature and stress interval the stress exponent n is constant. Further, the values of P91 steel correspond to published data on the creep behaviour of precipitation strengthened steels [1,5]. The high values of the stress exponent n probably involve internal stresses in addition to a power-law dependence of the flow rate with respect to an effective stress.…”

“…0.68Mo, 0.20V, 0.06Nb, 0.065N and 0.007Al with the following heat treatment: 1065°C/60 min/air + 750°C/120 min/air [4]. The Zr1%Nb cladding alloy has following chemical composition (wt.%): 1.0Nb, 0.05O, 0.01Fe and 0.01Hf [5]. After cold work processing the alloy was recrystallized.…”

“…8). 2) that all of creep tests were performed in the region of the power-law or dislocation creep (n ≥ 5) where creep is lattice diffusion controlled [4,5]. For given testing temperature and stress interval the stress exponent n is constant.…”

“…The paper aims to compare our recently published creep data obtained by both creep testing methods for two advanced creep-resistant materials, namely the advanced tempered martensite 9%Cr P91 steel (ASME Grade 91) [4] and a Zr1%Nb alloy [5], and to clarify the decisive factors causing observed differences in creep behaviour during the testing.…”