treyjay: Welding is such a highly visible yet niche arena of construction, that those who typically get pulled into welding-related technical arguments are routinely faced with four potential qualifications: PE, CWI, CWEng, and IWE.
Out of those four, PE's are typically valued the least, because most of the discussion surrounding welding, e.g. corrosion performance, NDE, creep properties, microstructures, etc, have almost nothing to do with "design" in the traditional sense as would be measured by a PE exam, excluding Ohio's Welding PE exam, which hasn't existed for many years now. The exception to this typically being a structural/mechanical firm that gets into issues over weld profiles or strength calcs, and not the processes or metallurgy behind it.
The CWI is a largely worthless title, but is thrown around as "I know everything, I'm a certified superinspector" more often than not, and management loves it.
The IWE, outside of the US, is the rock star of Welding Engineers, and is held in very high regard.
Very few people are CWEng's, so when you deal with a lot of AWS Code interpretation issues, debates over it's asinine conflicting rules (AWS Codes are a complete mess), the CWEng is a fantastic trump card that is often viewed with greater weight than the whiny superinspector. Again, management loves it, and it looks great on a resume if you're in welding engineering.
Relvinim: Check here:
http://www.aws.org/certification/docs/#N
There you will find links to the suggested reference materials, and also a link to B5.16, which is the document which covers the requirements and test sections for the CWEng exam.