Characterization of 304SS laser weld

unirrad_weld_char

We characterize the microstructure and mechanical properties of an AISI 304 stainless steel multi-pass laser weldment, made with 308 stainless steel filler material.  The aim of this work is to utilize microstructure and mechanical properties to precisely understand the extent and performance of the heat affected zone (HAZ) of the weld.

A full EBSD scan on the welded sample from the base through HAZ then to the filler was performed.  The results show a well-defined transition in the grain orientation and grain size from the base metal to the HAZ to the filler metal.  The average grain size of the HAZ is smaller than the grains in the base and filler metals, as evident from the EBSD scans.  The size of the HAZ is estimated to be around 3 mm. The grain orientation angle maps exhibit relatively average variation in each region, suggesting no notable texturing or alignment arises due to the welding process.  Transmission electron microscopic (TEM) analysis with energy-dispersive X-ray spectroscopy (EDX) reveals Cr-Si-O-C precipitates in the HAZ formed during the laser welding process.  Convergent Beam Electron Diffraction (CBED) reveals the amorphous nature of these precipitations.

This study of an unirradiated weldment will facilitate an understanding of the microstructures produced by laser welding, particularly in the HAZ, and may reveal underlying physics of the formation of the amorphous precipitation.  [Note this work is a component of a longer-term investigation into the mechanical integrity of laser weld repairs of highly irradiated, He-containing AISI 304 stainless steel under extended LWR service conditions, subject to further irradiation.]

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  1. K. Mao, Y.Q. Wu, and J.P. Wharry. EBSD and TEM analysis of the heat affected zone of laser welded AISI 304/308 stainless steel. Microscopy & Microanalysis, 23.S1 (2017) 2212.
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