摘要
Powder-based laser direct metal deposition(DMD),one of the directed energy deposition,was applied in air andunderwater to repair pre-machined NV E690 steel plates.Systematic investigations on the effects of underwaterenvironment and ambient pressures(0.01–0.35 MPa)on the microstructure evolution,phase transformation,andmechanical properties were conducted.The water quenching effect refined the grain size and increased thedislocation density and lath martensite content.The theoretical models of the underwater pressurized nitridingprocess and the precipitation kinetics of(Ti,V)N particles were established.Moreover,the microstructure evolution and the mechanical properties of other underwater DMD repaired samples did not show obvious relationwith the underwater ambient pressures.This investigation not only provides a candidate for the underwaterrestoration technique but also bridges marine engineering and emerging DMD technology.
基金
supported by the fund for the Technical Field of the Basic Strengthening Plan of Science and Technology of a Certain Commission of China(grant number 2021-JCJQ-JJ-0088 and 2022-JCJQ-JJ0117).
