轧辊表面激光重熔热障涂层抗热冲击性能研究

为了提高轧辊表面涂层的抗热冲击性能、延长其高温条件下的使用寿命,采用5kW CO2激光器,对轧辊表面等离子喷涂热障涂层进行了重熔处理。利用扫描电镜和能量色散谱仪,观察激光重熔涂层的涂层形貌和微观结构, 对分界面元素进行了微区成分分析。将试样在1000℃下保温10min后,放入常温(25℃)水中激冷,探究其抗热冲击性能,并与等离子喷涂涂层进行了对比。结果表明,经激光重熔后,涂层孔隙、裂纹明显减少,涂层质量明显提高;涂层与基体之间在一定程度上实现了冶金结合,结合强度明显提高;开始出现裂纹以及最终失效时的冲击循环次数由原来的14次和32次分别提高到43次和94次。该激光重熔工艺有助于提高涂层的热冲击性能,可延长轧辊的使用寿命。

Performance research of thermal shock resistance of laser remelting thermal barrier coating on roll surface

To improve the thermal shock resistance of roll surface coating and extend the service life under high temperature condition, plasma sprayed thermal barrier coating on the roll surface was remelted using 5kW CO2 laser. The coating surface morphology and microstructure of the laser remelting thermal barrier coating were observed by scanning electron microscopy. The micro-zone elements composition on the interface was analyzed by energy dispersive spectroscopy. By putting specimens at 1000℃ for 10min and then quenching into water directly, the thermal shock resistance was explored and compared with the plasma sprayed coating. The results show that porosity and crack of the laser remelting coating was reduced, and the quality of the coating was improved significantly. Metallurgical bonding was achieved between the coating and the substrate, and the adhesive strength was enhanced obviously. Thermal shock cycling times of the first crack and of the final failure was increased from 14 times and 32 times to 43 times and 94 times respectively. Laser remelting process is helpful to improve the thermal shock resistance of the coating and to extend the life of the roll.