Research On Surface Grain Ultra-refinement Technology And Structure And Property Of 3J33 Maraging Steel

In order to super-refine the surface grain of 3J33 maraging steel and improve surface wear resistance, the super-refining technologies, including cold rolling, shot pinning and laser surface quenching, are explored based on the effect of plastic deformation on recrystallization temperature, The 3J33 maraging steel surface grain super-refining is achieved by the cycle refinement combined with laser surface quenching, cold rolling followed by laser surface quenching, shot pinning followed by laser surface quenching, respectively. The microstructures of 3J33 maraging steel are investigated by the metallographic microscopic, scanning electron microscope(SEM), transmission electron microscope(TEM) and x-ray diffractometer(XRD), And the hardness and friction wear properties of 3J33 maraging steel treated with surface grain super-refining technology are evaluated.The results show that the grain is elongated along the rolling direction and the fibrous microstructure is obtained after the cold rolling treatment, Due to the work hardening, the hardness increases with increasing plastic deformation amount; The recrystallization temperature shows a decreases from 900℃at zero deformation to a stable value of 730℃at 80% deformation amount with increasing deformation degree.The combination of a large spraying pressure, a large diameter size of shot and a proper spraying time can get a surface plastic-deformation layer with large deformation intensity and depth, With the increase of the shot pinning time and pressure, the fibrous microstructure along a certain direction in the surface plastic deformation layer is replaced by equiaxed structure gradually, After shot pinning treatment, the microhardness value decreases with increasing the layer depth from surface, and become stable where the shot pinning effect is not obvious.For laser quenching, increasing laser output power and decreasing laser scanning rate can enhance the quenching depth. The combinations of laser quenching with cold-rolling, or with spraying, or with cycle-phase transformation, can super-refine surface grain. For the specimens after the cycle-phase transformation treatment, or cold-rolled with a large deformation amount, or spraying treatment, laser quenching with 1000W, 4800mm/min, three time can get the super-refined grain with 0.2μm~1μm diameter in the surface. The surface layer microhardness obviously increases to a value of about HV550kgf/mm~2.The surface grain super-refining can accelerate aging process, and enhance the surface hardness. The wear resistance of specimen treated by surface grain super-refining followed by aging is better than that of specimen without surface grain super-refining treatment.