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

摘要

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 degrees 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 mu m, composed of martensite and nano-Ti2N particles. After aging treatment, Ni-rich nano-precipitates (Ni-3(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 degrees 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.