Design of maraging steel with aluminum by laser metal deposition

In 18Ni300 maraging steel (MS) prepared by laser metal deposition (LMD), Ni3Al intermetallic compound is precipitated due to intrinsic heat treatment (IHT). Precipitation strengthening of the samples by IHT without further heat treatment is a prospective way to boost the mechanical behaviors of MS. The properties of the samples are represented by field emission scanning electron microscopy (FSEM), hardness measurement, tribological test, and potentiodynamic polarization test. The results indicate that these specimens are constituted by massive martensite, slight retained austenite, and intermetallic compounds. The hardness of the sample increases by 202 HV with the addition of Al. When the 6 at% atom Al is added, the sample with relatively good wear and corrosion resistance was obtained. When the Al concentration is 12%, the microstructure evolves from the equiaxed dendrite structure to coarse-grained martensite, which brings about the reduction of the mechanical properties of MS + 12 at.% Al.