Delaminations by Cleavage Cracking in Duplex Stainless Steels at Sub-zero Temperatures

Abstract

Impact toughness testing was conducted on 10 and 30 mm plates of 2205 together with a 30 mm plate of LDX 2101® duplex stainless steel (DSS). The testing temperatures were between 153 K (−120 °C) and room temperature. Interrupted fracture toughness tests of the 10 mm plate and a 50 mm plate of 2205 were also performed. The conclusion from the fractographic investigation was that the delaminations that occur in hot-rolled DSSs were cleavage fractures. The toughness anisotropy can be explained by the cleavage fracture and the appearance of the microstructure. The result from the interrupted fracture toughness test revealed that the delaminations initiated prior to the maximum force plateau and propagated ahead of the stable crack growth during testing. Estimated upper limit for the fracture delamination initiation toughness at sub-zero temperatures for the 2205 base metal according to the crack-tip opening displacement method was 28 to 61 μm for the 10 mm plate, 70 to 106 μm for the 30 mm plate and below 100 μm for the 50 mm plate.