Abstract: This paper describes the weld metal solidification-cracking and HAZ liquation-cracking in TIG welding of several kinds of superalloys used in jet engines.Experiments revealed that the cracking tendency became more serious as the Al,Ti and B contents of the alloys or the welding heat-input was increased;and that precipitation-hardening or work-hardening prior to welding made the alloys mores usceptible to hot cracking.