Mitigating the susceptibility to intergranular corrosion of alloy 625 by friction-stir welding

Abstract

In this work, friction-stir welding (FSW) was employed to alloy 625 grade I (soft annealed) sheets. Therefore, solid-state based welding was undertaken with a tool rotational speed of 200 rpm and a welding speed of 1 mm/s. Microstructural features were analyzed by light optical and scanning electron microscopy (LOM and SEM). Moreover, microhardness measurements were performed. The susceptibility to intergranular corrosion was verified by the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. Complementary, intergranular corrosion was also evaluated by the ASTM G28 Method A. FSW promoted grain refinement, increased microhardness, and reduction in the degree of sensitization. Finally, the mean corrosion rate observed in the ASTM G28 Method A test was 0.4406 mm/year, which suggests a good weld quality.

Effect of Supercritical Bending on the Mechanical & Tribological Properties of Inconel 625 Welded Using the Cold Metal Transfer Method on a 16Mo3 Steel Pipe

“…The main element used in this superalloy is Nickel. INCONEL ® uses the protected designation of a superalloy that is produced under the manufacturer Special Metals Corporation (New Hartford, NY, USA) [ 7 ], some other companies engaged in production or sales use their own designations such as: Haynes ® 625 [ 8 ], VDM ® Alloy 625 Nicrofer 6020 hMo [ 9 ], ATI 625TM [ 10 ], Alloy 625 [ 11 ], Altemp 625 [ 12 ], IN625 [ 13 ] or Inconel 625-0402 [ 14 ]. In the presented article, we will use the designation Inconel 625.…”

Quantitative analysis of susceptibility to intergranular corrosion in alloy 625 joined by friction stir welding

“…Therefore, it would benefit from a solid-state joining process. Friction stir welding (FSW) is an option to effectively avoid the problems caused by fusion welding since it occurs in solid state [1,[6][7][8][9].…”

“…Ni alloys are used in chemical, oil and gas, energy and aerospace industries because they have good resistance to oxidation and corrosion under severe conditions and excellent mechanical properties at elevated temperatures [1,2]. In particular, Alloy 625 is mainly used as a coating material in the oil and gas industry [1,3]. In most of these applications, fusion welding is employed for joining these components.…”