If you are experiencing gas inclusion in Hastelloy X welds made by GTAW, here are some guidelines :

(1) cleaning of joint preparation before welding with M.E.K. (*)
M.E.K. = Methy Ethyl Ketone (safest, cheapest and best cleaner for nickel alloys ; acetone will leave a thin film/layer on the metal that will vaporise into the weld pool)
(2) use a new pair of welding gloves , remove dirt / oil / ...
(3) don't use weld markers etc. on the weld
(4) lower the welding current , at high current the pool gets overheated and will include gaz
(5) if you're using a watercooled torch : take a look if ther's a little leak from where water can vaporize into the shielding gas

Don't blame the tungsten ...
Watch out with grinding dust from other metals (rust, carbon, dirt, grease, oil, ...) it may cause porosity and cracks