I'm not a smith, but a quick check of Wikipedia revealed the following information:
--Pure iron melts at 1538 deg. C
--Pure titanium melts at 1668 deg. C
That 90 deg. C difference in melting point difference is undoubtedly causing problems when trying to weld the two metals.
Another problem (found by web-searching) is that there are some issues with welding titanium, but apparently titanium can be welded to stainless steel (link
One answer may be to do some research on alloys. Then, create (or buy) a titanium alloy that has a melting point similar to that of an available steel alloy, and make the blade using materials that have similar thermal properties. I have no idea how tough such a blade would be. My guess is that it might be pretty soft.
Another possibility is to treat the keris as a piece of titanium jewelry, and not use steel at all. Titanium an be colored a variety of blue and purple shades through anodization, and such coloring can be done in fairly complex patterns, as searches on titanium jewelry on the web show. While it would be a "fake pamor," it might be simpler to shape the keris blade out of the titanium, then employ a titanium artist with the appropriate anodizing equipment to draw the pamor on. Obviously, such a blade wouldn't be a genuine pamored keris, but it could be gorgeous, depending on the skills of the artists involved.
My 0.0002 cents,