The martensitic strengthening of 12CrNi2 low-alloy steel using a novel scanning strategy during direct laser deposition

Nuclear power emergency diesel engine crankshafts are commonly fabricated using 12CrNi2 low-alloy steel. Direct laser deposition (DLD) may address conventional manufacturing issues associated with cost, long lead time, and design complexity. The idle time between deposited layers significantly affects the mechanical properties of the deposited materials. To date, the influence of inter-layer idle time on microstructural evolution and mechanical properties of DLD 12CrNi2 steel has not been studied in detail. In this study, we have designed different idle times between deposited layers or tracks to investigate the effect of idle time on the microstructural evolution and mechanical properties of DLD 12CrNi2 samples. The results indicate that sample S3 fabricated using a scanning strategy consisting of 10 s dwelling between tracks with 2 min between layers presented the most optimum combination of ultimate tensile strength (1007 MPa) and elongation (19.3%). This is mainly because sample S3 had a higher proportion of martensite due to the higher cooling rate of the upper layers than other samples. This paper provides experimental data and analysis to understand how the microstructural evolution and mechanical properties of DLD 12CrNi2 steel are impacted by different idle times between layers or tracks.