Surface Top Graphology,Corrosion and Microhardness of Oxygen Diffusion Hardened Pure Titanium Alloy TA4 after Laser Surface Melting

In the oxygen diffusion hardened condition,untreated and laser surface melted pure titanium alloy (TA4) by Nd:YAG pulsed laser,are hardened at temperatures of 650 to 700℃ with the end result being a passive,mechanically stable,abrasion resistant oxide ceramic rutile surface layer.The thickness of this surface layer depends on the time,temperature,and the microstructure of the Ti substrate.This paper describes the results of x-ray diffraction analysis,scanning electron microscope (SEM),microhardness measurements,and corrosion resistance measurements of hardened pure and laser treated Ti substrate.The oxygen diffusion hardened titanium alloy after laser surface melted samples (L-TA4) had a more pronounced grain structure and significantly higher roughness values than the untreated pure TA4 (U-TA4)samples.The L-TA4 samples also exhibited at least equivalent corrosion behavior and a definite increase in surface hardness compared to the U-TA4 samples.The results of this work suggest that laser surface melting plays a key role for effective oxygen diffusion hardening at 650-700℃ for pure and laser treated pure Ti alloys.

热氧化处理钛表面渗氧层的组织与性能研究

商业用纯钛在空气炉中700℃~900℃,1 h^4 h 进行热氧化处理,得到由氧化层和渗氧层构成的表面结构。通过金相观察、显微硬度测试、X 射线衍射(XRD)及扫描电镜(SEM)分析,研究了渗氧层的结构和性能。结果表明,经一定温度及时间处理,试样渗氧层被一条连续的界线分为内渗氧层和外渗氧层,在光学显微镜下观察,内外两层渗氧层形貌无差别,但在扫描电镜下观察可发现在较高温度形成的外渗氧层较疏松,内渗氧层则仍致密。随着热处理温度的升高、时间的延长,渗氧层厚度和含氧量增加,晶格常数c 伸长,表面硬度显著增大。

钛及钛合金的表面渗氧强化技术

钛及钛合金具有比强度高、耐蚀性好、良好的高温性及生物相容性等优点,是新兴的结构和功能材料,但由于其表面耐疲劳和耐磨损性能差等缺点使其应用受到限制。表面渗氧强化技术是提高钛合金表面性能的一种有效手段,本文综合评述了表面渗氧技术在钛及钛合金中的应用现状及研究进展。