Study on joining of orthodontic titanium-based materials using laser-welding

采用激光焊接0.016×0.022英寸β - ti、Ni-Ti和Co-Cr-Ni正畸丝，方法包括测量接头抗拉强度、测量激光穿透深度、用Micro-XRD测定金相以及用SEM检测显微组织。焊接在150至230 V的电压下进行。Ni-Ti组的平均抗拉强度显著低于其他大多数激光焊接组（P < 0.05）。虽然β - ti和Co-Cr-Ni的平均抗拉强度明显低于用银钎焊连接的对照标本，但足以用于临床使用。激光焊接后β - ti正畸丝的穿透深度比Ni-Ti和Co-Cr-Ni正畸丝深。从边界处2 mm处获得的激光焊接β - ti和Ni-Ti的微观xrd图与接收试样相似，表明保持了原始的显微组织。当输出电压为190 V或更高时，可能由于定向凝固效应，接头区域的大多数峰消失或变弱，SEM观察到焊接的β - ti中有细小的条纹。激光焊接β - ti和Co-Cr-Ni焊丝在临床上是可以接受的，因为接头有足够的强度，并且原始焊丝的冶金相没有很大的改变

Laser welding 0.016×0.022 inch beta-Ti, Ni-Ti and Co-Cr-Ni orthodontic wires was investigated by measuring joint tensile strength, measuring laser penetration depth, determining metallurgical phases using Micro-XRD, and examining microstructures with an SEM. Welding was performed at voltages from 150 to 230 V. Mean tensile strength for Ni-Ti groups was significantly lower (P < 0.05) than for most other groups of laser-welded specimens. Although mean tensile strength for beta-Ti and Co-Cr-Ni was significantly lower than for control specimens joined by silver soldering, it was sufficient for clinical use. The beta-Ti orthodontic wire showed deeper penetration depth from laser welding than the Ni-Ti and Co-Cr-Ni orthodontic wires. Micro-XRD patterns of laser-welded beta-Ti and Ni-Ti obtained 2 mm from the boundary were similar to as-received specimens, indicating that original microstructures were maintained. When output voltages of 190 V and higher were used, most peaks from joint areas disappeared or were much weaker, perhaps because of a directional solidification effect, evidenced by SEM observation of fine striations in welded beta-Ti. Laser welding beta-Ti and Co-Cr-Ni wires may be acceptable clinically, since joints had sufficient strength and metallurgical phases in the original wires were not greatly altered