Determination of creep properties of a P91 weldment by small punch testing and a new evaluation approach

Abstract

Local creep properties of a P91 weldment consisting of distinct zones, namely base metal, weld metal, as well as the fine-grained and the coarse-grained parts of the heat-affected zone were examined by Small Punch creep tests. Deflection vs. time graphs showed the zones' different creep resistances with that of the Heat Affected Zone-Fine Grained being lowest. Norton and Monkman-Grant type relations were established from Small Punch deflection curves for all zones. The evaluation of the Small Punch results was performed according to a new approach originating from the membrane stretching theory, as well as the method associated with the European Code of Practice for Small Punch Testing. The stress-rupture time results calculated by the new method were found to be very close to the Code of Practice's results with a similar amount of scatter, noting that with the new method, each Small Punch creep test is analyzed individually according to its observed deflection curve contrary to the Code of Practice method which disregards the actual deflection behaviour.