FATIGUE AND BRITTLE-DUCTILE TRANSFORMATION BEHAVIOR OF Al-Si COATING FOR NICKEL-BASE SUPERALLOY

摘要

The fatigue properties and the brittle-ductile transformation temperature (BDTT) of Al-Si coating for nickel-base superalloy have been investigated in a high temperature microscopy with loading equipment . It was found that brittle-ductile transformation temperature of Al-Si coating is proportional with Al and Si contents. The microhardness of outer layer is apparently inferior to that of inner layer for Al-Si coating because the Si element diffuse into inner layer during heat treatment, which induces the high microhardness of inner layer. The brittle fracture took place in Al-Si coating of nickel-base superalloy and the fatigue cracks initiated rapidly at the initial stage of fatigue testing when temperature TBDTT, the superficial cracks initiated slowly and the fatigue behavior has been improved because the plastic deformation of coating is superior to that of the bulk material.