LAUSR

A nanostructured nitride layer is produced on a large titanium plate using mechanical shot peening (MSP) followed by a low-temperature gaseous nitriding method. The combined effect of the MSP and low-temperature nitriding on the microstructural evolution and mechanical properties is investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, as well as hardness, wear resistance, and toughness tests. The results of the characterization are compared to a coarse-grained specimen produced by a standard nitriding process. The results show that a nitride layer with a thickness of 10–15 µm is produced on the MSP-treated Ti plate after nitriding at 550 °C for 5 h. The nitride layer is composed of nanostructured ϵ-TiN and γ-Ti2N phases with a high supersaturation of nitrogen. The nitriding kinetics is significantly enhanced by the nanocrystalline structure. The surface hardness, thickness of the hardened layer, and wear resistance of the nitrided MSP Ti plate are all enhanced relative to the coarse-grained nitrided sample. The toughness of the nanostructured nitrides is greatly improved compared with the conventional nitrided specimen.