EXAMINATION OF EMBRITTLED CARBON-STEEL BOILER TUBE BY A SCANNING AUGER MICROPROBE

The embrittlement of carbon steel seamless tube of a power plant boile r after extended service of 34,000 h at 346 degrees C under 15.68 MPa has been studied by scanning Auger microprobe. The segregation of N at grain boundaries and also the segregation of P at grain boundaries an d part of the cleavage planes after long term service caused the embri ttlement of carbon steel and resulted in the explosion of the boiler f eedwater pipes. The N/Al atomic ratio can be used to determine the age ing embrittlement tendency of carbon steel during long time service at 350 degrees C, and when the N/Al atomic ratio is approximately 1 or l ess, the embrittlement can be avoided.