Effects of aging time on the microstructure and mechanical properties of laser-cladded 18Ni300 maraging steel

Abstract

In this work, 18Ni300 maraging steel was successfully fabricated, for the first time, by a laser cladding technique under atmospheric condition. The effects of different aging times (1, 3, 6, and 9 h) at 500 °C on the microstructure and mechanical properties of the as-cladded 18Ni300 maraging steel were carefully characterized and analyzed. The microhardness and tensile strength increase with increasing aging time up to 6 h, and subsequently, decrease with the time extending to 9 h. On the contrary, the elongation is shown a reverse trend. The original 18Ni300 maraging steel exhibits cellular microstructure with an average grain size of 2 µm, composed of martensite and nano-Ti2N particles. After aging treatment, Ni-rich nano-precipitates (Ni3(Mo,Ti) and Ni(Mo,Ti)) together with reverted austenite were formed and promoted with the extension of aging time. The optimal comprehensive performance of the 18Ni300 maraging steel can be obtained by aging 3 h at 500°C, with microhardness of 509 HV0.2, ultimate tensile strength of 1686 MPa, and elongation of 11.5%, respectively. The microstructural mechanisms accounting for the property changes are discussed in detail.