Experimental and Numerical Investigations on the Creep Behaviour of Heat-Resisting Chromium Steel X10CrMoVnb9-1 by Means of Small Punch Test

Abstract

The mechanical characterisation of materials at operating temperatures is of great importance for many industrial branches. Miniaturised specimens are required if the available amount of material is not sufficient for standard sized samples. For that reason, a material testing device is presented, which allows the mechanical investigation of round plate small scale specimens at temperatures up to 1273 K. Modern high temperature materials for nuclear power plant components of the next generation are subjected to temperatures above 873 K. A constant long-term exposure at this temperature level results in creep of the material. The reduction of the creep tendency of heat-resisting chromium steel X10CrMoVNb9-1 (P91) is achieved by temperature stable carbides and carbonitrides at the grain and sub-grain boundaries. However, this ensures no absolute inhibition of creep. In the present investigation the high temperature small punch test (HT-SPT) is used to experimentally and numerically characterise the creep behaviour of P91. The experimental part includes the performance and evaluation of HT-SPT creep tests at constant force (creep rupture tests) at different temperature and load levels without clamping of the samples. The numerical part covers the identification of Norton creep parameters by numerical optimisation based on a calibration of finite element simulated and experimentally obtained creep curve results for the material P91. For the microstructure evaluation of the steel P91, a pre and post mortem investigation of the HT-SPT creep specimens is performed by light optical microscopy (LOM), scanning electron microscopy (SEM), energy-dispersive X-ray microanalysis (EDX), and an oxalic acid test.