Effects ofVadditiononimprovementofheatshockresistanceand.pdf

Wear 302 (2013) 1444–1452Contents lists available at SciVerse ScienceDirectWear0043-16 http://d n Corr E-mjournal homepage: /locate/wearEffects of V addition on improvement of heat shock resistance and wear resistance of Ni–Cr–Mo cast steel brake disc N. Harada a,n, M. Takuma b, M. Tsujikawa c, K. Higashi c a Kurimoto Ltd., Shibatani 8-45 Shibatani 2-chome, Suminoe-ku, Osaka-shi 559-0021, Japan b Kansai University, Yamatecho 3-35, Suita-shi 564–8680, Japan c Osaka Prefecture University, Gakuen-cho 1-1, Naka-ku, Sakai-shi 599-8531, Japana r t i c l e i n f o Article history: Received 10 October 2012 Received in revised form 10 January 2013 Accepted 12 January 2013 Available online 29 January 2013 Keywords: Brake disc Bainite Heat shock resistance Wear resistance Hardenability48/$ - see front matter 2013 Elsevier B.V. A /10.1016/j.wear.2013.01.029 esponding author. Tel.: t81 6 6686 3235; fax ail address: no_harada@kurimoto.co.jp (N. Haa b s t r a c t It is important to improve the heat shock resistance and wear resistance of discs for railway cars for long-term and safe use. We have studied the effects of additional elements on the heat shock resistance of Ni–Cr–Mo steel used for the production of brake discs. In this paper, the effects of V addition on Ni–Cr–Mo steel are discussed. It was clarified that the hardness near the friction surface is as high as that of high hardenability steel, and the heat shock resistance is improved by the addition of 0.1% V. It was also determined that V addition prompted a transformation to lower bainite, which has high toughness and hardness. 2013 Elsevier B.V. All rights reserved.1. Introduction Ni–Cr–Mo steels with relatively high martensite hardenability (hereinafter referred to as hardenability), such as A4340, which are used for the discs of brakes in railway cars moving at high speeds above 300 km/h, have little heat shock resistance. Recently, the maximum commercial speed and braking load for railway cars has continued to in