Abstract: Nickel-based alloys exhibit excellent corrosion resistance for oilfield services but are restricted for abrasive wear service due to a lack of surface hardness. Nitriding and boronizing can improve wear resistance, however, the effects of these surface treatments are still not fully understood. In this investigation, nitriding and boronizing are applied on four nickel-based alloys, specifically Alloys 925 (UNS N09925), 935 (UNS N09935), 718 (UNS N07718), and 625+ (UNS N07716) to understand and measure their effects on corrosion. Corrosion was evaluated by various independent testing with sodium chloride, including crevice corrosion immersion, salt spray, and cyclic potentio-dynamic polarization. This investigation shows that nitriding and boronizing both reduce the corrosion resistance of nickel-based alloys. Boronizing provides thicker hard layers than nitriding, but also downgrades the corrosion resistance the most, as observed repeatedly and measured through three different tests.
Authors: Virendra Singh and Manuel Marya
Keywords: Nickel-based alloys, nitriding, boronizing, crevice corrosion, salt spray, cyclic potentio-dynamic polarization