The microstructural development in a Type 309 stainless steel weldment associated with a post-weld heat treatment of 30 h at 580°C has been studied using analytical electron microscopy (AEM). The purpose of post-weld thermal treatments is generally to relieve stresses within the weld, thereby improving performance. Microstructural stability during these thermal treatments is important for the weld; i.e., no deleterious phases should form. in this example, detailed microstructural analyses of a weldment in the as-welded and postweld heat-treated condition have been performed. Microstructural analyses were performed using Philips CM 12 and CM300-FEG analytical electron microscopes equipped with Oxford Instruments ISIS analyzers and LZ5 energy dispersive x-ray spectrometers, and a CM200-FEG analytical electron microscope equipped with a Gatan Image Filter (GIF).
As-Welded Condition:The microstructure of the weld was characterized by the presence of dislocated austenite (γ) and a network of delta (δ) ferrite.