TRIBOLOGICAL PROPERTIES OF TITANIUM-ALLOYS

Titanium is often the most cost-effective corrosion-resistant material for applications in the chemical process industry that involve resistance to halides. Unfortunately, there are usually some components in these systems that involve relative sliding-titanium tribosystems - eg. bolts and nuts, valves, piping connections, etc. Titanium and its alloys have had a reputation for poor tribocharacteristics, but detailed information on suitable counterfaces and wear specifics is scarce. This paper summarizes a study conducted on the two most widely used titanium alloys, Grade 2 commercially pure titanium and the age-hardenable Ti6Al4V. Dry sand-rubber wheel tests were conducted to assess abrasion resistance; fretting, galling and reciprocating pin-on-plane tests were conducted to determine if there is a "best" counterface for these two titanium alloys. The test results are distilled into recommendations for use of titanium alloys in tribosystems in the chemical process industry. Both alloys have poor abrasion resistance. Grade 2 pure titanium should be avoided in all titanium tribosystems and there are preferred counterfaces for the Ti6Al4V alloy, but the best metal-to-metal wear resistance is obtained when the alloy is anodized and coated with a dry film lubricant.