Liquid mercury can be a natural component of natural gas, condensate, and crude oil production streams, so the potential for liquid metal embrittlement (LME) of hydrocarbon production metallic components must be considered. With increasing use of titanium alloys for deep sour high pressure/high temperature well oil country tubular goods (OCTG) and dynamic offshore riser components, titanium’s ability to resist degradation from liquid mercury contact warranted assessment under relevant hydrocarbon production conditions. The results of exposing UNS R56404 forging and pipe product forms to liquid mercury over the 25°-232°C temperature range while highly stressed at and beyond the alloy’s yield point via three differing loading modes are reported. These included sustained load 90 day C-ring tests, slow strain rate tensile testing, and rippled slow strain rate cyclic tensile loading. Although excessive plastic strain can allow substrate Ti metal wetting and low energy subcritical crack growth (i.e., LME), results confirm that titanium’s robust, non-mercury wetting surface oxide film is key to providing LME resistance to substantial plastic strain limits and beyond a reasonable range of surface mechanical damage expected in service.
Key words: titanium, titanium alloy, liquid metal, mercury, liquid metal embrittlement, rippled slow strain rate