激光熔覆原位自生Ti(C;N)陶瓷涂层的热力学理论及工艺

利用500 W脉冲YAG激光作为辐射源,纯氮气作为氮化元素,粒度为20μm的钛粉和石墨粉为预涂粉末,采用激光熔覆原位自生的方法,在Ti-6Al-4V表面制备出优良的Ti(C,N)陶瓷涂层.通过热力学分析,并结合XRD分析方法,研究了原位自生Ti(C,N)的反应机理以及工艺参数(包括脉冲频率、脉冲宽度、扫描速度等)对原位自生Ti(C,N)陶瓷涂层的影响.热力学分析结果表明,在激光辐射条件下,可原位生成以Ti(C,N)为主的陶瓷涂层.XRD分析表明,合适的工艺组合为:氮气压强为0.4 MPa,离焦量为15 mm,扫描速度在2.0～4.0 mm/s之间,脉冲频率为15 Hz,脉宽在3.0 ms左右....

Thermodynamical and Technological Studies on In-situ Self-Generating Ti(C,N) Ceramic Coating via Laser Cladding

The in-situ self-generating Ti(C, N) ceramic coating prepared on the surface of Ti-6Al-4V alloy by laser cladding (LC) deposition was investigated, where a 500 W pulsed YAG laser was used as radiation source with the 99%-purity N2 used for nitrogenation and the titanium powder (particle size 20 μm) mixed with powdered graphite used as the precursor. The effects of the in-situ self-generating reaction mechanism and such process parameters as pulse width, pulse frequency and scanning speed on the coating were studied by thermodynamic analysis in combination with XRD. XRD results showed that the main phases of the coating are TiC0.3N0.7 and TiN or TiN0.3, and that the appropriate process parameters include the pulse frequency 15 Hz, pulse width around 3.0 ms, scanning speed in the range from 2.0 to 4.0 mm/s, N2 pressure 0.4 MPa and defocus distance 15 mm. The metallographic results showed that the dendrite structure is dominant in the coating and distributed quite uniformly, and that the ceramic coating is bonded well to the substrate.