Microstructure and properties of laser-borided composite layers formed on commercially pure titanium

详细信息    查看全文

• 作者：M. Kulka ; N. Makuch ; P. Dziarski ; A. Piasecki ; A. Miklaszewski
• 关键词：Laser-boriding of pure titanium ; Microstructure ; Abrasive wear resistance
• 刊名：Optics and Laser Technology
• 出版年：March, 2014
• 年：2014
• 卷：56
• 期：Complete
• 页码：409-424
• 全文大小：12372 K

文摘

Laser-boriding was proposed in order to produce composite boride layers on commercially pure titanium. Three zones were observed in the microstructure: laser-borided re-melted zone (TiB, TiB₂ and Ti_{伪鈥?/sub>-phase), heat affected zone (Ti伪鈥?/sub>-phase) and the substrate without heat treatment (Ti伪-phase). The stick-like titanium borides occurred in the re-melted zone. In some areas, the tubular nature of titanium borides was visible. Among the sticks of titanium borides the needles of Ti伪鈥?/sub>-phase appeared. The high overlapping of multiple laser tracks (86%) caused the formation of uniform laser-alloyed layer in respect of the thickness. The microcracks and pores were not detected in the laser-borided composite layer. The high hardness of the re-melted zone (1250-1650 HV) was obtained. The hardness gradually decreased up to 250-300 HV in heat affected zone and up to about 200 HV in the substrate. In case of higher laser beam power used (1.95 kW), the re-melted zone was thicker and more homogeneous in respect of the microstructure and hardness. The craters obtained at the surface after the Rockwell C indentation test evidently revealed ideal cohesion of the laser-borided layer (HF1 standard). The significant increase in wear resistance of laser-borided composite layers was observed in comparison with commercially pure titanium. The lower mass wear intensity factors were obtained for laser-alloyed layers. The measurements of relative mass loss were also used in order to evaluate wear behavior of the investigated materials. The tests of laser-borided layers showed the catastrophic wear of the counter-specimens. The separated particles of counter-sample caused the accelerated wear of the laser-alloyed specimen. The longer duration of the tests, carried out without the change in a counter-specimen, caused the adhesion of counter-sample particles on the laser-borided specimen. The increased contact surface was the reason for the higher temperature and created the favourable conditions for this adhesive wear.}