I've TIG welded titanium with argon. No problems. In fact, I've never used any other shielding gas in mt TIG welding experience.
From what I've read, helium gives better penetration when TIG welding thicker sections of aluminum, but I've never TIG welded any aluminum over 1/4" thick. Argon has always worked for me. Argon also produces a smoother arc, from what I've read.
Also, from what I've read, helium is not a complete dead-end. Alpha emitting radioisotopes (like uranium and thorium) emit helium nuclei. Capture two electrons, and you've got a helium atom.
This phenomenon is used in
helium dating.