Deformation behavior of laser welds in high temperature oxidation resistant Fe–Cr–Al alloys for fuel cladding applications

Abstract

Ferritic-structured Fe-Cr-Al alloys are being developed and show promise as oxidation resistant accident tolerant light water reactor fuel cladding. This study focuses on investigating the weldability and post-weld mechanical behavior of three model alloys in a range of Fe-(13-17.5)Cr-(3-4.4)Al (wt.%) with a minor addition of yttrium using modern laser-welding techniques. A detailed study on the mechanical performance of bead-on-plate welds using subsized, flat dog-bone tensile specimens and digital image correlation (DIC) has been carried out to determine the performance of welds as a function of alloy composition. Results indicated a reduction in the yield strength within the fusion zone compared to the base metal. Yield strength reduction was found to be primarily constrained to the fusion zone due to grain coarsening with a less severe reduction in the heat affected zone. For all proposed alloys, laser welding resulted in a defect free weld devoid of cracking or inclusions.

A combined APT and SANS investigation of α′ phase precipitation in neutron-irradiated model FeCrAl alloys

“…These alloys are presently under consideration for accident tolerant fuel cladding applications because of their superior performance in steam environments compared with Zr-based alloys, which often exacerbate loss-of-coolant accident conditions as a result of hydrogen gas generation and exothermic oxidation reactions [4,5]. Current research eorts are focused on developing an optimized candidate FeCrAl alloy that maximizes high-temperature aqueous corrosion and oxidation resistance [6] while maintaining adequate performance with respect to mechanical properties [79], processability [7,10], radiation tolerance [1115] and neutronics [16,17].…”

Database on Performance of Neutron Irradiated FeCrAl Alloys

“…The alloys that have undergone neutron irradiation and radiation tolerance screening include Generation I, Generation II, and commercial FeCrAl alloys. Generation I alloys are ORNL developed model FeCrAl alloys with Y additions used to screen primary composition effects (Cr and Al) on radiation tolerance, as well as other key performance aspects such as welding [21], oxidation [4,9,22], burst behavior [23], and corrosion [24]. Generation I alloys are otherwise referenced as B-series alloys or model alloys in previous reports [3,[5][6][7][8][9][10][11][12][13][14][15][16].…”

“…These Phase I alloys have demonstrated that higher Cr and Al contents are generally more desirable for maximizing corrosion and/or oxidation resistance but too much of either can limit alloy applications; excessive Cr additions increase the formation of embrittling Cr-rich αʹ precipitates [17][18][19], while high Al content results in failure during the seamless tube extrusion process required for LWR cladding fabrication [20]. Weldability was shown to have little dependence on composition when using controlled fusion welding techniques [21]. PIE efforts on Phase I materials have demonstrated that irradiation accelerates the formation of αʹ phase precipitates in addition to forming dislocation loop structures, which both contribute to radiation-induced hardening that increases in severity with dose, though the impact of irradiation temperature was not evaluated [17].…”

Experimental Plan and Irradiation Target Design for FeCrAl Embrittlement Screening Tests Conducted Using the High Flux Isotope Reactor

“…The focus is to develop a fully ferritic FeCrAl alloy that can be produced by conventional manufacturing methods (casting and tube drawing) and exhibit high temperature oxidation resistance. Other favorable properties currently being optimized include formability, mechanical properties, weldability, and radiation tolerance [2][3][4][5][6][7][8][9][10]. Recent work under this program has established preliminary data on the radiation tolerance of four model FeCrAl alloys (Fe-10Cr-4.8Al, Fe-12Cr-4.4Al, Fe-15Cr-3.9Al, and Fe-18Cr-2.9Al) irradiated to 1.8 dpa at 382°C in the HFIR [3].…”