Y.L. Yang
,
D. Zhang
,
H.S. Kou
,
C.S. Liu
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null
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null
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null
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null
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null
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null
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null
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null
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null
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null
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null
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null
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金属学报(英文版)
Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs (OM). The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm / s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm - 2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2, and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80?滋m, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.
关键词:
laser cladding
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null
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null
Y.L. Yang
金属学报(英文版)
The mixing technology of laser and heated nitrogen was applied to improve the surface hardness of titanium alloy (TC4). The samples were nitrided with laser power density of 6.5×105W·cm-2, the scanning speed various from 100 to 500mm·min-1. The nitrogen gas was pre-heated to 300℃ to accelerate the nitriding process. Some interested samples were tested with XRD method (X-ray diffraction) to analyze the composition of nitrides, and the surface hardness of HV was measured. The results show that TiN and Ti2N were formed on the surface of Ti alloy with proper nitriding parameters, but TiN is the main composition. The surface hardness increased by three times, which is from the original value of 269 to 794kg·mm-2. The mechanism of the mixing technology is considered mainly of the activation of nitrogen by laser power and the pre-heated process which accelerated the nitriding process. The nitridation process can be considered as six steps given in detail. The result by analyzing the mechanism of improving the surface property of TiAl alloy shows the improvement of surface property due to two factors: the first reason is the result of laser annealing, and the second one is the formation of TiN.
关键词:
laser nitridation
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表面硬度
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钛合金
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X射线衍射
Y.L. Yang
,
C.S. Liu
,
F.J. Sun
,
D. Zhang
金属学报(英文版)
CW-CO2 laser nitriding technique was applied to improve the properties (such as aging property and the core loss) of grain oriented silicon steel. The samples were nitrided with regular space. Laser power density and scanning speed were chosen as 7.8×105W·cm-2 and 100mm·min-1. By some laser irradiation, Fe4N and Fe3N were formed in the nitrided zone. The nitrided samples were annealed at the temperatures ranged from 100 to 900°C. The core loss of some interested samples was tested. The results show that the core loss of the nitrided samples with different thickness of 0.23 and 0.30mm decreased by 14.9% and 9.4% respectively, and the aging property were improved up to 800°C. The mechanism of laser nitriding to improve the properties of grain oriented silicon steel is discussed.
关键词:
laser nitriding
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null
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