Vinothkumar Thilla Sekar, Kandaswamy Deivanayagam, Prabhakaran Gopalakrishnan, Rajadurai Arunachalam
Department of Conservative Dentistry and Endodontics, Faculty of Dental Sciences of Sri Ramachandra University, Chennai, Tamil Nadu, India.
Department of Mechanical Engineering, Velammal Engineering College, Chennai, Tamil Nadu, India.
Eur J Dent. 2015 Oct-Dec;9(4):513-517. doi: 10.4103/1305-7456.172626.
The aim of this study is to investigate the role of dry cryogenic treatment (CT) temperature and time on the Vickers hardness and wear resistance of new martensitic shape memory (SM) nickel-titanium (NiTi) alloy. The null hypothesis tested was that there is no difference in Vickers hardness and wear resistance between SM NiTi alloys following CT under two soaking temperatures and times.
The composition and the phase transformation behavior of the alloy were examined by X-ray energy dispersive spectroscopy and differential scanning calorimetry, respectively. Fifteen cylindrical specimens and 50 sheet specimens were subjected to different CT conditions: Deep cryogenic treatment (DCT) 24 group: -185°C, 24 h; DCT six group: -185°C, 6 h; shallow cryogenic treatment (SCT) 24 group: -80°C, 24 h; SCT six group: -80°C, 6 h; and control group. Wear resistance was assessed from weight loss before and after reciprocatory wet sliding wear.
The as-received SM NiTi alloy contained 50.8 wt% nickel and possessed austenite finish temperature (Af) of 45.76°C. Reduction in Vickers hardness of specimens in DCT 24 group was highly significant (P < 0.01; Tukey's honest significant difference [HSD]). The weight loss was significantly higher in DCT 24 group (P < 0.05; Tukey's HSD).
Deep dry CT with 24 h soaking period significantly reduces the hardness and wear resistance of SM NiTi alloy.
本研究旨在探究低温干处理（CT）的温度和时间对新型马氏体形状记忆（SM）镍钛（NiTi）合金维氏硬度和耐磨性的影响。所检验的零假设为，在两种保温温度和时间条件下进行CT处理后，SM NiTi合金的维氏硬度和耐磨性不存在差异。
分别通过X射线能谱和差示扫描量热法对合金的成分和相变行为进行检测。15个圆柱形试样和50个片状试样接受不同的CT处理条件：深冷处理（DCT）24小时组：-185°C，24小时；DCT 6小时组：-185°C，6小时；浅冷处理（SCT）24小时组：-80°C，24小时；SCT 6小时组：-80°C，6小时；以及对照组。通过往复式湿滑动磨损前后的重量损失评估耐磨性。
所接收的SM NiTi合金含50.8 wt%的镍，奥氏体终了温度（Af）为45.76°C。DCT 24小时组试样的维氏硬度降低极为显著（P < 0.01；Tukey真实显著差异[HSD]）。DCT 24小时组的重量损失显著更高（P < 0.05；Tukey's HSD）。
浸泡24小时的深度低温干处理显著降低了SM NiTi合金的硬度和耐磨性。
