Fracture toughness of ISO 3183 X80M (API 5L X80) steel friction stir welds

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Friction stir welding (FSW) is a solid-state joining process with numerous advantages such as good dimensional stability and repeatability, which is widely used Al alloys and with a great potential for critical joining applications involving high melting temperature alloys. Twelve millimeter thick plates of ISO 3183 X80M (API 5L X80) steel was friction stir welded using two passes on both sides of the plate using ceramic tools. Different heat inputs were obtained using a fix travel (welding) speed in combination with several spindle speeds. The fracture toughness of the two-pass joints was evaluated at 25 degrees C using the critical crack tip opening displacement (CTOD(m)), revealing that joints produced with lower spindle speeds presented higher toughness at the heat-affected zone (HAZ) and stir zone (SZ), which are comparable with the base metal (BM) toughness. On the other hand, joints produced using higher spindle speeds presented low fracture toughness at the SZ and elevated CTOD(m) toughness at the HAZ. The joints produced with low spindle speeds showed CTOD(m)-values above the offshore standard (DNV-OS-F101) requirements. (C) 2010 Elsevier Ltd. All rights reserved.7715SI29372945FINEPLNLSConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PetrobrasConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Improvement of cavitation erosion resistance of a duplex stainless steel through friction stir processing (FSP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The cavitation erosion (CE) resistance of an UNS S32205 duplex stainless steel (DSS) was improved through microstructural modification using friction stir processing (FSP). As-received material was processed using 200 rpm and 100 mm/min spindle and travel speeds, respectively. The cavitation erosion tests were performed in a vibratory apparatus according to ASTM G32 standard. The incubation period, the maximum erosion rate and the variation of surface roughness during the tests are reported and the results are compared with those obtained for the base metal samples (BMS). The worn surfaces were characterized using roughness measurements and scanning electron microscopy (SEM). After a CE testing time of 10 h, FSP samples showed a 70% diminution of the mass loss when compared to the BMS. Moreover, a 200% enhancement of incubation time and 100% reduction in the erosion rate were achieved after FPS. The improvement of CE performance is related to the recrystallized and refined microstructure, as well as to the modification of the elongated alpha/gamma interfaces. (C) 2012 Elsevier B.V. All rights reserved.297416719981005Colciencias [349]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)LNNanoPetrobrasFinepConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Colciencias [349