Titanium and Niobium cannot be soldered, so I am told.
So, short of Fusion Welding, Jewelers 2-part Epoxy seems to be the only alternative for bonding these elements.
There are 2 concerns regarding Epoxy Resin.
First, and foremost, is the fact that Epoxy Resin is an allergen causing agent in itself. Although not everyone suffers from Allergic Contact Dermatitis/Eczema, those of us who do, seem to be prone to react to a specified list of items. Epoxy Resin is one of them.
This means, in jewelry design, it is important that no Epoxy touch the skin. Although it is acceptable under governmental code (even in California), to label a pierced earring “hypo-allergenic” if at least, the post itself contains no allergen causing agents, the fact is, it’s not just the post that comes into “contact” with our skin.
Second, it is difficult to adhere Titanium and Niobium with Epoxy Resin. But I have found that attention to certain details seems to be the answer for success.
* The larger the two surfaces to be bonded, the more secure the bond.
* Etch the two surfaces well. Epoxy needs nooks and crannies to create a place to bond. I usually do this with needle files, in a cross hatch fashion. Filing in both directions creates an etching effect, as opposed to filing in one direction which creates a buffed effect.
* Remove all dirt, debre, and skin oils from the surfaces to be adhered. Rubbing alcohol works fine for this.
* 2-part Epoxies contain Resin, and Hardener. It’s important to use equal amounts of each. I use a paper plate and squeeze equal sized drops of each, next to one and other. Give it a moment to make sure that the two liquids (which are different in consistency to each other) are actually equal. Then I mix well with a toothpick, and apply evenly to one of the surfaces.
* I then have 5 minutes to set the second surface, press into place, and remove any excess (with a dampened cloth.
* I usually let this cure under a lamp for 12 hours. Then test the adhesion by trying to remove the two components from one and other. If it doesn’t come apart, I consider it a success. If it does come apart, it usually means that I didn’t etch the surfaces well enough.
Follow up care to the finished piece should include the following considerations. Don’t soak the piece for any length of time. Don’t use harsh chemicals on the piece. Both of these actions can loosen the epoxy.
The Mrtitanium Forum 
All the online articles I can find about epoxy allergic reactions have to do with either the uncured resin, or the hardening agent. I couldn’t find anything about reactions to properly cured epoxy.
One suggestion: After hardening, wipe the surface of the epoxy with acetone. I use a Q-tip. This will remove traces of unhardened resin or excess hardener from the surface without significantly (noticeably) affecting the polymerized mass.
Back in my radiation research days, I used a 5:1 epoxy in the lab. We’d measure out five parts of resin, and then one part of hardener on a lab scale. We’d then mix well, pour, and put on a hot plate for 10 minutes to set it.
When I bond to titanium, I scratch the titanium surface that will be hidden with a needle file or a small burr on a flex shaft (Dremel equivalent) just before gluing.
I never considered the possibility that the properties of the resin and/or the hardener, that cause allergic reactions, could change once cured. I assume that like Water and Ice are still H2O.?.?.
This is an interested concept and definately worth more research.
I currently use Devcon 2 part Epoxy. Both the Epoxy Resin, and the Hardener bottles contain the warning “Potential Skin Sensitizer”.
Usually, when I research Allergic Contact Dermatitis/Eczema, I search those words specifically. I’m then taken to Medical Specialty sites that provide information.
Here are a couple of sites that I refer to on my own site.
http://www.eczema-ltd.com/contact.php
http://www.eczemaguide.com/eczema_basics/eczema_like/contact_dermatitis.html
http://www.mayoclinic.com/health/dermatitis-eczema/DS00339
http://en.wikipedia.org/wiki/Dermatitis
Besides epoxy, there is an industrial polystyrene bonding agent that works well on these metals. http://www.Reactivemetals.com sells it as E6000 adhesive.
Here’s a list of other E6000 providers online
i am allergic to epoxy resin and have rash on hands and arms is there anythink i use to heal it ?
As with any rash, cortisone ointments and antihistamines are the best over-the-counter treatments. If a rash persists, do see a doctor.
It has recently been found that those people who suffer with Allergic Contact Dermatitis (ACD) are also prong to be allergic to certain other chemicals. Unfortunately, even the ointments and medications we are given to heal our ACD contain these chemicals! http://www.wear-earrings-again.com/research2.html
Your best bet is to get back to basics. Use NOTHING on your skin that you wouldn’t put into your eyes! No anti-biotic ointments, or harsh chemicals. Use no soaps which have fregrances in them including laundry soaps on your clothes. Instead, use fresh water to clean, you can add sea salt to the water to control itching, dry well with a soft cloth (this is key), and use a petroleum jelly to lubricate only if needed to help heal cracked bleeding skin (a tiny bit goes a long way).
If this doesn’t heal things up for you, go to a Dermatologist. General practitioners are not qualified to treat your allergies. They are not up to date with the current new findings regarding irritants and allergies that effect our skin.
prong = prone (sorry)