It is possible to braze, using pure silver filler metal and special flux, and it is also possible to stick weld using a small diameter stainless rod, BUT.... Both processes, especially on 18 gauge, are very difficult to join without the finished project looking like crap. You'll have problems with blow throughs, incomplete fusion, warpage, and slag removal. The last time I tried to braze stainless, I stomped away so frustrated that I swore I'd never do it again...that was 15 years ago...
Unless you are a First class, A #1 top notch Welder with a lot of patience, I recommend an alternative, such as pop-rivits.
Good Luck!!