Abstract
In present study, Si addition (1.0at%) is found to be responsible for a dramatic improvement in high temperature oxidation resistance of 4th generation superalloys; this might be attributed to an increase in Al activity induced by Si to promote the formation of protective Al 2 O 3 layer and improved adhesion between the Al 2 O 3 and the substrate due to the presence of Si. However, there are debits associated with Si addition in terms of reduction in both heat-treatment window and microstructare stability. The National Institute for Materials Science has developed two experimental Si-bearing 4 th generation superalloys that exhibit an excellent balance of resistances against mechanical deformation and environmental attack; their temperature capability of both creep and oxidation properties have reached an average of +40°C over CMSX-4. Hence, the cost-performance of 4 th generation superalloys can potentially be improved by addition of Si. The present article aims to quantify the properties of these experimental Si-bearing compositions in order to aid the future development of new superalloys with Si additions.