Detection of intergranular embrittlement of reactor pressure vessel steel by electrochemical method

摘要

The reactor pressure vessel (RPV) steel, with manganese-nickel-molybdenum (Mn-Ni-Mo) alloying, was subjected to accelerated thermal aging treatment at 450 °C for durations upto 8400 h. Impact toughness decreased and the intergranular fracture (IGF) increased monotonically with increased aging time. This was accompanied by insignificant changes in average hardness, grain size, misorientation and carbide size. However, electrochemical polarisation tests in picric acid showed increasing width of attack at prior austenitic grain boundaries (PAGB). It was hypothesized that the accelerated aging led to phosphorus segregation at the grain boundary, a hypothesis supported by the post electrochemical attack on the PAGB, leading to a significant loss in impact properties.