激光熔覆原位自生TiB_2的工艺研究

Study on the Technology of Insitu-fabrication of TiB_2 by Laser Cladding

采用固体YAG脉冲激光对预置一定配比的Ti/B混合粉末涂层进行激光熔覆,在TC4钛合金表面原位合成TiB_2陶瓷增强相。利用X射线衍射、金相显微观察以及显微硬度测试等手段,分别对熔覆样品的物相、组织形貌和显微硬度分布特征进行了研究。实验结果表明,激光功率为64W(其中电流140A,脉宽8～10ms,频率12～15Hz),扫描速度1.0～1.2mm/s,离焦量2mm时,可原位生成TiB_2陶瓷涂层。金相观察结果表明,熔覆层与基体结合处为波形界面,形成了良好的冶金结合。显微硬度沿截面纵向呈梯度分布,熔覆层的硬度较基底平均提高了3～4倍。

TiB2 enhancement ceramic phase was insitu-fabricated by laser cladding Ti/B compound powders on the surface of titanium alloy by using YAG laser. Phase constituents, morphology and the microhardness were characterized using X-ray diffraction, optical microscope and microhardness tester. The results show that the ideal parameters to insitu-fabricate TiB2 ceramic coating is laser power of 64 W （decided by current of 140A, pulse width 8 to 10 ms, and pulse repetition 12 to 15 Hz）, laser scan speed of 1.0 to 1.2 mm/s, and defocus length of 2mm. A metallurgical bonding between the coating and the substrate was formed. Typical dendrites were observed in the coated zone. The microhardness from the surface of the coating to the substrate displays a gradient distribution. The microhardness in coated zone is as much as 3 to 4 times than that of the substrate.