Effect of heat treatment on microstructure and residual stress fields of a weld multilayer austenitic steel clad

Abstract

Samples of ferritic–perlitic steel were cladded by submerged arc welding with three layers of two austenitic stainless steel filler metals. After the weld cladding, samples were submitted to stress relief heat treatment (SRHT) under different parameters. The characterization of the microstructure of the samples was made by optical and scanning electron microscopy, and the residual stresses determined by X-ray diffraction and incremental hole drilling method. The results were compared and related to the SRHT conditions. The microstructure of the third layer of the as-welded clad consists of cellular austenite and intercellular eutectic delta-ferrite particles, while the microstructure of the first layer presents a high proportion of lathy martensite in γ-Fe cells. The second layer contains a low proportion of martensite and high proportion of austenite. The SRHTs induced partial decomposition of delta-ferrite in the superficial layer, increasing the rate of decomposition with the treatment temperature, and the coarsening of precipitates in the vicinity of the interface carbon steel–stainless steel. The superficial layer of the as-welded and machined clad plate presented residual compressive stresses. The SRHT at 540°C, for 10h of holding time, enabled some residual stress relaxation, unlike the treatment at 620°C, during 1h, which increased the compressive stresses.