Abstract: Spray forming technique has been applied to prepare 18Ni(250) maraging steel+10%Al₂O₃ particulate reinforced metal matrix composite. The spray deposited preform shows high density and favourite microstructures such as homogeneous distribution of the reinforcement particulates and free from interface reaction. Compared with the matrix 18Ni maraging steeh the composite demonstrated an accelerated aging behaviour. After heat treatment, the composite material shows a tensile strength near the matrix steel, with much improved wear resistance. Nanoindentation investigation of the aging process of the composite material shows that there exists a sharp distribution of elastic modulus and microhardness around Al₂O₃ particulates, which can be attributed to the distribution of precipitate caused by the thermal misfit dislocation distributions.