title: Effect of dry cryogenic treatment on Vickers hardness and wear resistance of new martensitic shape memory nickel-titanium alloy.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  Deep dry CT with 24 h soaking period significantly reduces the hardness and wear resistance of SM NiTi alloy.
authors.affiliation: Department of Conservative Dentistry and Endodontics, Faculty of Dental Sciences of Sri Ramachandra University, Chennai, Tamil Nadu, India.
authors.forename: Thilla Sekar
authors.initials: TS
authors.lastname: Vinothkumar
authors.affiliation: Department of Conservative Dentistry and Endodontics, Faculty of Dental Sciences of Sri Ramachandra University, Chennai, Tamil Nadu, India.
authors.forename: Deivanayagam
authors.initials: D
authors.lastname: Kandaswamy
authors.affiliation: Department of Mechanical Engineering, Velammal Engineering College, Chennai, Tamil Nadu, India.
authors.forename: Gopalakrishnan
authors.initials: G
authors.lastname: Prabhakaran
authors.affiliation: Department of Production Technology, MIT Campus, Anna University, Chennai, Tamil Nadu, India.
authors.forename: Arunachalam
authors.initials: A
authors.lastname: Rajadurai
keywords: Cryogenic treatment; Vickers hardness; nickel-titanium; shape memory; wear resistance