Development of Creep Damage in Steel Grades X10CrMoVNb9-1 (P/T 91) and X20CrMoV12-1

摘要

The demand for higher efficiencies has initiated the development of new high strength steels for application in power plants. Besides the well-known X10CrMoVNb9-1 (P/T 91) more advanced steels like E 911 and P/T 92 have now been qualified for commercial use. All these new steels belong to the same group of martensitic chromium-rich steels as X20CrMoV12-1 which has been in service for almost 40 years. In view of the large amount of test results, it was decided to investigate the damage behaviour of X20CrMoV12-1 and X10CrMoVNb9-1 (P/T 91) being representative for the whole group. The damage behaviour of both steel grades shows great similarities to the behaviour of low alloyed ferritic steels. A correlation exists between the appearance of creep damage and the decrease of rupture ductility. Creep cavities are formed on former austenite grain boundaries as well as on martensite lath boundaries. With respect to light microscopy creep damage can first be detected at the beginning of tertiary creep, which is related to a life consumption t/t_R～0.5. Long-time tests are in progress with rupture times around 10~5h. These tests are carried out in order to clarify whether the results from short-time tests can be transferred to service-like conditions.