If you are a degreed welding engineer I doubt the CWI credential is going to add a lot of benefit to your resume. However, if you are a welding engineer because your employer hung that shingle under your nameplate beside your cubical, it would add some some credibility to your status.
I'm not trying to be smart with my last comment. I have been introduced to a number of welding engineers over the years that had no engineering degree of any kind or they had very little if any experience, background, or knowledge of welding. They were assigned their position because the corporate management thought they needed a welding engineer and so they filled the position. In one case the only qualification the engineer had was that he owned a "buzz box", but freely admitted he didn't know how to weld. Someone gave it to him because he tinkered with cars. Someone in the company got wind that he had a welder, so "he clearly knew about welding".
Best regards - Al