Fracture toughness of the alloy CA6NM quenched and tempered and of its welded joint without PWHT

摘要

abstract_textpThe steel CA6NM quenched and tempered is used in rotors of hydraulic turbines, pumps and compressors. The objective of this work is to quantify the fracture toughness of the alloy CA6NM quenched and tempered, and in its welded joint without post-welded heat treatment (PWHT). For that purpose, CT specimens are machined from pieces of the alloy CA6NM for toughness evaluation of the alloy used in a hydraulic turbine. Because of the elastoplastic condition of the material, the specimens are tested using the J integral concept, being raised the curve of resistance J-R and characterized the crack initiation J(1C). For the welded joint without PWHT the brittleness of the joint did not allow the assessment of the curve J-R in the CT specimens, and the toughness is characterized with the KC concept. The welding procedure considers the conditions of a probable repair of erosion by cavitation in the turbine, where the PWHT is not viable. The results confirm the high toughness for the steel CA6NM, with values approximately three times larger than the obtained ones in the welded joint without PWHT The results confirm the high toughness for the steel CA6NM, with values approximately three times larger than the obtained ones in the welded joint without PWHT In terms of the fracture, the steel CA6NM presents a ductile behavior and the welded joint without TTPS a brittle behavior/p/abstract_text