Failure analysis on the bolt fracture of pressure control valve in power plant

A bolt of an intermediate pressure stream control valve in a power plant was broken. Through macro inspection, chemical composition analysis, mechanical analysis and metallographic analysis of the broken bolt, it is shown that the microstructure and grains of the bolt have been deteriorated during long-term high temperature operation, which results in the degradation of the mechanical properties of the material, and finally brittle fracture occurred.