Okay, so the triangular patch of the lock bar around the detent is a different color/finish because of carburization, not carbidization.
My limited understanding of carburization is that it is a form of heat treatment that hardens steel by allowing it to absorb, into it's surface, carbon from a sacrificial carbon source such as charcoal. This sounds a lot like how carbon was added to iron in ancient blacksmithing.
Googling seems to indicate that the term "carbidize" is used almost entirely by the knife industry, or at least I can't find any other sources of the term. The descriptions of the carbidizing tool that you can buy on various knife maker sites, describes it as a process of layering the titanium with tungsten from a sacrificial tungsten rod. Sounds sort of like tig welding without the inert gas or filler rod.
http://link.springer.com/article/10.3103/S0967091209060072
I did find this scientific journal, which I'm not going to buy, but you can read the first couple pages for free. The sample pages seem to indicate that carburizing titanium results in carbidizing the titanium with a layer of graphite/carbon. So it almost sounds like carburizing titanium could be categorized as a subset of carbidizing, using high-temp carbon transfer rather than plasma arcing tungsten. Except, the seeming lack of carbidizing as a general industry term makes me question my little hierarchy. Whatever. As usual googling increases my knowledge and confusion at the same time.
Whatever the case, it seems likely that CRK's invoice line item of heat treating the lock is really re-carburizing the lock-bar face. So from the various responses on this thread, it seems like depending on what is required to "tune" the lock, CRK will merely adjust lock bar tension, re-carburize the lock face (and I suspect tweak the lock-face of the blade tang as needed), or entirely replace the lock-side scale (and tweak the lock-face of the blade tang as needed).
Haha, mystery solved?
