Abstract
Precipitation-hardening stainless steels are iron-nickel-chromium alloys containing precipitation hardening elements such as aluminum, titanium, niobium, and copper. In this work, heat treatment of a novel precipitation hardening stainless steel using niobium as a forming element for the hardening precipitates was carried out in order to increase its hardness. The steel composition was 0.03C - 0.22Si - 17.86Cr - 3.91Ni - 2.19Mo - 1.96Nb (in wt.%). The samples were solution annealed at 1100°C for 2 h. Cooling was done in oil and the samples were subsequently aged at 500, 550, and 600°C. The solution annealed samples exhibited an average hardness of 30 Hardness Rockwell–Scale C and after the aging treatments, the hardness increased to 46 HRC. The hardness increases during the aging treatments were very fast. A 5 min treatment achieved hardness levels that were close to the maximum obtained for this alloy. Niobium was an efficient precipitation hardeners forming a Laves phase of the type Fe2Nb.
