FAILURE ANALYSIS OF WELD-REPAIRED B-1900 TURBINE BLADE SHROUDS

摘要

Four turbine blades having a nominal B-1900 composition weresubmitted for failure analysis after cracks were detected or Znotchfailure had occurred at the shroud. The blades were weldrepaired at the shroud edges and returned to service, only to failafter several hours. The blade repairs involved machining awaythe original material, and then inert gas tungsten arc weldrepairing with a Co-base hardface and B-1900 filler alloy.Analysis of the broken blades found that they had failed fromfatigue. This fatigue was the result of cracks in the heat-affectedzones of the blades created from liquation at the grain boundariesand residual stresses that could not be relieved through the lowductilityweldments. Cracks also developed from precipitation ofbrittle secondary phases at the coating-weldment interdiffusionzone.