1. When heat treating titanium medical components, should I be concerned about surface contamination?
YES! Surface contamination of titanium is typically caused by the presence of oxygen, nitrogen, and/or carbon gas while the titanium is at an elevated temperature. It’s permanent unless removed mechanically or chemically. It can lead to fracture and component failure in service if not removed.
2. Is there a heat treating temperature at which surface contamination starts to be a concern?
AMS 2801, a widely used aerospace specification for processing titanium parts, requires one surface contamination test be performed on a sample from all heat treatments hotter than 1,000°F, even in vacuum. Although this is a widely used threshold, design engineers of medical components should always carefully consider the risk of surface contamination caused by heat treating.
3. I have a finished titanium medical component and I need it heat treated. What do I do?
Find a heat-treat supplier that knows the risks and has the right tools for the job. Not just any vacuum furnace will be sufficient. The chosen heat-treat supplier will have an all-metal hot zone vacuum furnace capable of operating at a pressure near 1x10-6 Torr.That supplier should also have MedAccred certification for processing titanium medical components.
4. How can I test for surface contamination on my titanium medical components?
Again, find a laboratory that is accredited by MedAccred to perform the test. MedAccred approval comes only after an intense audit which tests the competency of the laboratory performing the test. Any laboratory that is MedAccred authorized (for the specific test) is your best bet.
5. I want to join titanium to 304 stainless steel and copper with a hermetic seal, can that be done?
YES! Titanium may be effectively vacuum brazed to both of those materials, and others, to produce a hermetic seal easily capable of a leak rate less than 1x10-9 standard cubic centimeters per second of helium at one atmosphere pressure differential. That leak rate would take 32 years to pass 1cm3 of helium gas. There may be size limitations for brazing based on the coefficient of thermal expansion of the materials being joined, however, effective braze joints are made on titanium medical assemblies using the vacuum brazing process.
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