激光熔覆-激光气体氮化方法制取TiCN-TiN复合熔覆层

Preparation of TiCN-TiN Compound Cladding by LC-LGN Technology

采用500W YAG脉冲激光作为辐射源,TiCN粉末为熔覆材料,高纯N2气作为氮化元素和保护气体,利用激光熔覆-激光气体氮化(LC-LGN)方法,在钛合金(Ti-6Al-4V)表面制备了以TiCN和TiN为主的复合熔覆层.研究了激光工艺参数对TiCN-TiN复合熔覆层成分的影响.对熔覆样品进行了XRD物相分析和显微硬度测试.结果表明:在激光功率和脉冲宽度一定的条件下,脉冲频率、扫描速度是影响TiCN-TiN复合层形成的主要因素.合适的工艺参数组合为:脉冲频率为15 Hz,脉宽为3.0 ms,扫描速度为2.0 mm/s.扫描速度小于2.0 mm/s时,熔覆过程中氧化现象严重,而高于2.0 mm/s时熔覆层与基底结合不够牢固,易出现脱落现象.处理后,样品的显微硬度由原始3.3 GPa提高到14 GPa(HV0.2)左右,显微硬度提高了近4倍.

TiCN-TiN compound cladding was prepared on the surface of the titanium alloy Ti- 6Al-4V using the LC-LGN （laser cladding-laser gas nitriding） technology, where the 500 W pulsed YAG laser was taken as the irradiation source with the TiCN powder whose particle size is 3μm as remelting material and highly pure N2 which is coaxial with laser beam as shielding gas/ nitriding element. The influence of laser parameters on the preparation of TiCN-TiN compound cladding was investigated experimently with XRD and micro Vickers. The results showed that the pulse frequency and scanning velocity are the main influencing factors on the formation of TiCN-TiN cladding when the laser power density and pulse width remain unchanged. It was revealed that the appropriate process parameters are the pulse frequency 15 Hz, pulse width 3.0 ms and scanning velocity 2.0 mm/s. Heavy oxidation is found in cladding process if the velocity is lower than 2.0 mm/s and the cladding will peel off due to low binding strength between it and substrate if higher than 2.0 mm/s. After such cladding treatment, the samples＇ microhardness HVo.2 of TiCN-TiN compound increase to about 14 GPa from 3.3 GPa without cladding, i.e., about 4 times higher than that of substrate.