Tribological performance of surface engineered low-cost beta titanium alloy

Research output: Contribution to journalArticlepeer-review

Authors

Colleges, School and Institutes

Abstract

Low-cost beta (LCB) alloy (Ti-6.8Mo-4.5Fe-1.5Al) is developed specifically for non-aerospace (e.g. automotive and motor sports) applications. However, as for all other titanium alloys, LCB alloy is characterised by a high and unstable coefficient of friction and a strong scuffing tendency. Hence, a new surface engineering process based on optimal integration of bulk heat treatment with surface ceramic conversion has been developed, and this paper reports the tribological performance of surface engineered LBC titanium alloy. TEM analysis carried out on the microstructure of the ceramic conversion layer. Reciprocating pin-on-disc sliding wear tests were conducted against both WC and hardened steel balls under unlubricated and oil lubricated conditions. Post-examination of the wear tracks, counterparts and wear debris was carried out to investigate the wear mechanisms involved.
The experimental results show that the wear resistance of the LCB alloy can be improved by 4-16 times by the novel combined bulk/surface treatment; the coefficient of friction is reduced from 0.8-1.0 for the untreated material to 0.2-0.4 for the treated samples. The wear mechanisms evolve from severe adhesive wear for the untreated material to mild abrasive wear for the treated material when sliding against a WC-Co ball in air. However, severe wear to the steel counterpart occurred and hence large frictional forces formed, which led to delamination wear of treated surfaces. It is also interesting to find that oil lubrication cannot reduce but rather increases the wear of treated surfaces especially when sliding against a hardened steel ball mainly due to oil pressure induced delamination wear.

Details

Original languageEnglish
Pages (from-to)952-960
Number of pages9
JournalWear
Volume426-427
Issue numberPart B
Early online date10 Apr 2019
Publication statusPublished - 30 Apr 2019

Keywords

  • Ceramic conversion, Combined bulk and surface treatment, Low-cost beta alloy, Reciprocating sliding wear, Solution & ageing