Effect of In-Situ Ti2N on Microstructure and Properties of SAF2906 Duplex Stainless Steel Fabricated by Laser Melting Deposition

SAF2906 Duplex Stainless Steel (DSS) was fabricated by powder prepasted Laser Melting Deposition(LMD). The formation of ferrite was promoted by increasing the molybdenum content. The volume ratio of ferrite and austenite of LMDed SAF2906 DSS with 3 wt% molybdenum content reached 4:6. The effects of 2 wt% and 4 wt% nano TiN addition on the microstructure and comprehensive properties of LMDed SAF2906 DSS were investigated in detail. The results showed that in-situ generated nano (10 nm similar to 100 nm) and submicron (100 nm similar to 1 mu m) Ti2N particles were uniformly distributed in the LMDed SAF2906 DSS matrix, and some nano Ti2N particles preferred to be distributed among grain boundaries. The primary and secondary dendrite spacing of austenite of LMDed SAF2906 with 4wt% TiN addition decreased by 48% and 62%, respectively, while the austenite content increased by 15%. The wear resistance, strength, elongation and corrosion resistance of the LMDed SAF2906 were gradually improved with the increase of nano TiN addition from 0 to 4 wt%. The average microhardness for the sample with 4 wt% nano TiN addition (381 HV0.2) was 1.2 times that of the sample without TiN (326 HV0.2), while the wear rate (9.12 x 10(-13) m(3)/Nm) was only 71% that of the sample without TiN (1.28 x 10(-12) m(3)/Nm). The yield strength, tensile strength and elongation of the LMDed SAF2906 with 4wt% TiN addition increased to 801 MPa, 1028 MPa and 31.8%, respectively. The self-corrosion potential increased to 0.0216 V, and the self-corrosion current density also reached 4.57 x 10(-7) A center dot cm(-2) for LMDed SAF2906 with 4wt% TiN addition.