Heat Treatment of Precipitation-Hardening Stainless Steels Alloyed with Niobium

摘要

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 in order to increase its surface hardness and wear resistance was performed. The steel composition was 0.03 C -0.22Si - 17.86Cr - 3.91Ni - 2.19Mo - 1.96Nb (in wt%). The samples were solubilized at 1100 °C for 2 hours. Cooling was done in oil and the samples were subsequently aged at 500, 550 and 600 °C. The solubilized samples exhibited an average hardness of 30 HRc and after the aging treatments, the hardness increased to 46 HRc. The hardness increases during the aging treatments were very fast. A 5 minute 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 Fe_2Nb.