A comparative analysis of metallurgical and mechanical properties of friction welded and post weld heat treated (oil quenched) duplex stainless steel joints

The effects of post weld heat treatment (PWHT) and oil quenching on the metallurgical and mechanical properties of the duplex (UNS 531803) welded joints were evaluated at three different temperatures namely 1080, 1150 and 1200 degrees C. The microstructural variation, austenite/ferrite phase changes, grain size measurements and microhardness aspects of the welded joint were observed. The fraction of ferrite and austenite phases was equivalent at 1150 degrees C. Nickel element was more efficient in controlling the twin phase balance. Finer grain structure was achieved at 1150 degrees C due to recrystallization effect. Twin phase presence and absence of precipitates were confirmed through XRD and TEM which followed Kurdjumov-Sachs relationship. At a heating pressure of 40 MPa, heating time of 4 s, an upsetting pressure of 80 MPa, and an upsetting time of 2 s during a PWHT at 1150 degrees C, a 50/50 balance between the duplex phases, fine grains, and increased microhardness were obtained.