A method of replacing a damaged blade (12A) of an integrally bladed rotor assembly (10) including a disc (14) and a plurality of blades (12) extending outwardly from the disc (14) includes the steps of; removing the damaged blade (12A) to leave a blade stub (16) projecting from the disc (14); depositing a collar (22) of metal around the blade stub (16) at a position physically separated from the disc (14); attaching a replacement blade (12B) to the stub (16) by linear friction welding; and removing the collar (22). A body (20) of a material may be deposited between the disc (14) and the collar (22) to protect the disc (14) from damage.