What was found
(CAN) PWC SB 1430 EMBODIED AT LAST OVERHAUL WITH WRONG TYPE OF SEAM WELD COMPLETED. SB CALLS FOR RESISTANCE SEAM OR STITCH WELD TO BE ACCOMPLISHED IN ORDER TO WELD THE INNER LINER TO THE EXHAUST DUCT. IN THIS CASE A TIG WELD WAS COMPLETED WHICH CAUSED THE DUCT TO CRACK ADJACENT TO THE WELD. SUBMITTER STATES THIS TYPE OF CRACKING IS DANGEROUS IF NOT SPOTTED. IT COULD CAUSE THE EXHAUST DUCT TO FAIL AND CAUSE A CATASTROPHIC FAILURE OF THE ENGINE.