Wide-Gap Braze Repair of Single Crystal Aerospace Superalloys

Wide-Gap Braze Repair of Single Crystal Aerospace Superalloys

 Advanced alloy design and improved solidification processing techniques have resulted in the development of single crystal (SC) precipitation strengthened nickel-base superalloys for manufacturing higher performance aero-engine components. Nevertheless, the developments that have occurred with SC aerospace superalloys in the past two decades have not been matched by adequate understanding of appropriate techniques for repair and joining components made from these materials. SC nickel-base superalloys components are extremely difficult to repair by conventional fusion welding processes due to their high susceptibility to cracking during welding and post-weld thermal treatments. Wide-gap brazing, involving the use of powder mixture of base-alloy and braze-alloy as filler material, is an attractive alternate technique for repairing difficult-to-weld structural materials. Unfortunately, application of this technique to SC nickel-base superalloys has been severely limited due to detrimental formation of stray-grains within repaired region, which compromises elevated temperature performance. In this research, numerical simulation coupled with careful experimental work was used to study how to prevent the formation of stray-grains in SC nickel-base superalloys wide-gap brazement. The results of the research, which will be presented and discussed, have now produced an effective approach for repairing SC nickel-base superalloys by wide-gap brazing technique, without the deleterious formation of stray-grains, while also ensuring reduction in the processing time.