ON THE LASER ADDITIVE MANUFACTURING REPAIR OF UNS S41000, UNS S17400 AND UNS S32750 BY UNS N06625

摘要

The laser powder-fed deposition of Alloy 625 (UNS N06625) on three corrosion-resistant ferrous alloys, martensitic stainless steel UNS S41000 (410), precipitation-hardened martensitic stainless steel UNS S17400 (17-4PH), and superduplex stainless steel UNS S32750 (2507) has been investigated to evaluate additive manufacturing (AM) as a repair process for oilfield service parts. Compared to industrial cladding, deposition by laser powder-fed AM is more controlled and therefore offers promise for minimizing base material-powder chemical dilution, base-material heat-affected zone, and improving part in-service properties. To match requirements of alternative and competitive coating repair processes, in this investigation, all AM deposits were made of only two cross-hatched layers with total thickness between 200 to 400μm. These AM deposits were specifically achieved with a customized powder-fed CLAD? AM system (France) utilizing pre-established deposition parameters; i.e., 180W beam power, 600 and 800 mm/min scan speeds, 0.5-mm scan overlaps. Through micro-hardness surveys, metallographic examinations, and EDS elemental mapping, this investigation establishes that dense, uniform, hard (-300 HVN), crack-free, and UNS N06625 compliant deposits of fine dendritic structures may be produced on all three stainless steels. However, with the exception of UNS S32750 (2507), a large martensitic hardening occurred in both the UNS S41000 (410) and UNS S17400 (17-4PH) stainless steels. Although inconsequential for many service tools, this hard sublayer (500 HVN on UNS S41000; 370 HVN on UNS S17400) remains a major concern for corrosive service equipment, where environmentally-assisted cracking could threaten structural integrity.