Must be for high temp service, haven't had any experience with cobalt in that high of a percentage.

I would advise you to contact the provider of the material for compatible filler metals and recommended welding procedures.

Inco Alloys International, Inc. (Huntington, WV) deals with exotic materials containing cobalt.

Complementing robert's answer, inco's website is www.inco.com
Enter it and make a search on cobalt.
Giovanni S. Crisi
Sao Paulo - Brazil

I worked with a lot of Kovar when I was in the jet turbine business.  It is cobalt based but we did not weld to ASME.  We had our own in house vendor specs.

Are you talking about something like this?

http://www.specialmetals.com/documents/Udimet%20alloy%20L-605.pdf

If it is, then look at this link and you'll probably find what you're looking for:

http://www.specialmetals.com/products/index.php

Here's the home page:

http://www.specialmetals.com/index.php

Look under "products" to find out more information, and look under "contacts" to get in touch with them.

BTW, it's called: "Special Metals Corporation" in the USA nowadays gentlemen.

Here's another link which covers some cobalt based alloys weldability:

http://www.welding-advisers.com/Welding-cobalt.html

Is it Haynes 25 (L-605) the alloy you're describing?

Here's a commentary from Walter Sperko's site:

"A new family of alloys, UNS R31233, has been added to the P-number listing as P-
49. This is a cobalt-based alloy with 26% chromium, 9% nickel, 5% molybdenum,
iron and tungsten., Nickel and cobalt are interchangeable from a weldability viewpoint,
so this alloy fits in the general category of the other nickel alloys. Interestingly,
the Subcommittee elected to skip P-numbers 47 and 48 to leave room for new
“true” nickel alloys."

"For those with internet access, finding the P or S-number of a base metal can be
done at www.pnumbers.com. This site is not an ASME-sanctioned site, but it contains
a table of all the metals listed in QW/QB-422. This table can be sorted by any
column in QW/QB-422 (i.e., by specification, grade, P-number, product form, etc.).
There is also a site www.fnumbers.com that covers filler metals."

Page 6 of 8 in this .pdf:

http://www.sperkoengineering.com/html/articles/2004_addenda.pdf

Respectfully,
Henry

No wonder you can't get an answer! You incorrectly described the alloy in your initial query, and you must include more details regarding your welding process & procedures:

"looking in the region of just over 50% cobalt, 10% nickel and 20 - 30% chromium."

Now GTD 222 is made up of this:

                              Metric              English
Carbon, C           0.080 - 0.12 %    0.080 - 0.12 % 
Chromium, Cr       22.2 - 22.8 %     22.2 - 22.8 % 
Cobalt, Co          18.5 - 19.5 %     18.5 - 19.5 % 
Manganese, Mn   <= 0.10 %          <= 0.10 % 
Nickel, Ni            55.03 - 57.42 %  55.03 - 57.42 % 
Silicon, Si           <= 0.25 %          <= 0.25 % 
Tungsten, W       1.80 - 2.20 %      1.80 - 2.20 %

Which means that Nickel is @ over 50% in this alloy now known as: GTD 222 which is a "Centri-Vac Nickel Cobalt Alloy..." Here's the link from "MatWeb:"

http://www.matweb.com/search/datasheet.aspx?matguid=705da93caed547be8ebe479a1c440f6f&ckck=1

Now, you might be able to match a similar super alloy in this chart listed in the .pdf below with GTD222 by comparing the chemical compositions shown in each alloy found in the chart.

http://www.sulzerts.com/portaldata/5/Resources//resourcecenter/toolsforyou/Super_Alloy_Compositions_.pdf

Here's another set of links which may also be helpful:

http://www.c-mgroup.com/vacuum_melt_index/nickel_base_equiax.htm

http://www.c-mgroup.com/vacuum_melt_index/equiax_xref.htm

Check out the patent for GTD 222 in this .pdf and read it carefully as it compares the chemical compositions of a few similar nickel alloy version which are slightly different in %'s of specific elements:

http://www.freepatentsonline.com/7014723.pdf

Here's the starting page for this patent:

http://www.freepatentsonline.com/7014723.html

Here's another very interesting patent regarding the use of GTD 222:

http://www.freepatentsonline.com/20110024393.pdf

Here's the start page for the same patent:

http://www.freepatentsonline.com/y2011/0024393.html

Another interesting patent:

http://ip.com/pdf/patapp/US20110062220.pdf

And another one:

http://www.freepatentsonline.com/7278828.pdf

One more:

http://www.freepatentsonline.com/20110042361.pdf

Start page:

http://www.freepatentsonline.com/y2011/0042361.html

Finally here's the last patent I found referring to welding of GTD 222:

http://www.patents.com/us-6652677.html

Here's a very good and informative paper from NASA titled:Tensile Properties of Weldments in Alloy GTD 222. For example, here's an excerpt:

"The two GTD 222 vendors were Teledyne Alvac and Carlton Forge Works/Special Metals. Teledyne Alvac
supplied rolled bar with two different cross sections, L-shaped about 1.4 in. high, 0.9 in. along the base, and 0.4 in.
thick, and “hat”-shaped which were essentially rectangular, 0.5 by 1.2 in. Carlton Forge supplied a rolled ring about
1.5 in. wide radially and 0.9 in. thick. Rolling procedures were not divulged.
All the materials were solution treated before welding. The Teledyne Alvac GTD 222 was solution treated at
either 1800 or 2200 °F for 1 hr, yielding ASTM grain sizes of 9-10 or 2-3, respectively. The Carlton Forge material
was solution treated at either 2100 or 2200 °F for 1 hr, but both temperatures yielded an ASTM 2-3 grain size."

This information comes from the .pdf listed below:

http://gltrs.grc.nasa.gov/reports/1996/TM-107271.pdf

You can also buy this article from the ASME Library for $25.00 USD:

"Nickel-Base Alloy GTD-222, a New Gas Turbine Nozzle Alloy"
J. Eng. Gas Turbines Power  -- January 1993 --  Volume 115,  Issue 1, 155 (5 pages) Here's the link:

http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000115000001000155000001&idtype=cvips&gifs=yes&ref=no

Here's another interesting paper also:

http://iweb.tms.org/SUP/superalloys2000/01-4771-721.pdf

Here's .pdf covering the MSDS of a brand of welding filler for GTD 222:

http://polymet.thomasnet.com/Asset/pmet823.pdf

You also may want to get in touch with this gentleman Named David A. Moore who wrote this paper for presentation titled:
“Wrought GTD-222: A New Structural Alloy for Gas Turbines,” ASM International Advanced Aerospace Materials/Processes Conference, Anaheim, California (1993).

Here's his CV:

http://www.unified-eng.com/people/mooreCV.html

Go to this link to download a .pdf from the Wood Group covering repair methods for various types of turbine components including weld repairs on GTD 222:

http://wamp.tavanir.org.ir/getFile/?id=6D760D923B1642D0D016F18B1F481762

Here's an interesting article from Liburdi:

http://www.liburdi.com/TurbineServices/Articles/Newsletters/Increasing%20Life%20Through%20Repair.pdf

This also is from Liburdi via ASME Turbo Expo 2009
Gas Turbine Technical Congress & Exposition
June 8-12, 2009, Orlando, Florida, USA:

http://www.liburdi.com/LiburdiEngineering/analysis-life/White%20Papers/PRACTICAL%20EXPERIENCE%20WITH%20THE%20DEVELOPMENT%20OF%20SUPERALLOY%20REJUVENATION%20%20GT2009-59444.pdf

This one is from the Dept of Energy:

http://www.netl.doe.gov/technologies/coalpower/turbines/refshelf/handbook/4.4.1.pdf

Here's some Russian research of these GTD nickel alloys:

http://www.omkb.ru/english/pages/news/termostabilnost.htm

These are from one of my favorite sites... University of Cambridge Department of Material Sciences & Metallurgy in the UK:

http://www.msm.cam.ac.uk/phase-trans/2002/papers/APNickelWeldv2.pdf

http://www.msm.cam.ac.uk/phase-trans/2002/papers/Babu1.pdf

This one is an oldie, but goodie from NASA:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19950004780_1995104780.pdf

I threw this in because it's a fascinating article in itself:

http://www.tms.org/pubs/journals/JOM/0306/David-0306.html

Another good article:

http://site.ge-energy.com/prod_serv/products/tech_docs/en/downloads/ger3957b.pdf

Another interesting article nonetheless:

http://www.camelottech.com/CMFiles/Docs/Fuels%20Flexibility%20in%20Heavy%20Duty%20Gas%20Turbines.pdf

This one explains Laser Powder Fusion Welding:

http://www.huffmancorp.com/downloads/white_papers/LPFWcolor_Kaser.pdf

From Pratt & Whitney:

http://www.pw.utc.com/media_center/assets/pwps_igt_f7a_nozzles.pdf

http://www.prattwhitney.mobi/power_systems/Frame_7FA+e_Nozzles.html

More from GE who patented GTD 222:

http://site.ge-energy.com/prod_serv/products/tech_docs/en/downloads/ger4171.pdf

This one is from Combined Cycle Journal:

http://www.combinedcyclejournal.com/4Q2009/CCJ_24-31.pdf

This alloy, Nimonic 263 is similar to GTD 222, and is made by Special Metals Corporation:

http://www.specialmetals.com/documents/Nimonic%20alloy%20263.pdf

Another similar alloy from Special metals:

http://www.specialmetals.com/documents/Nimonic%20alloy%2090.pdf

Here's their line of high performance alloys:

http://www.specialmetals.com/products/index.php

And this one as well:

http://www.specialmetals.com/documents/Inconel%20alloy%20740.pdf

And these too:

http://www.specialmetals.com/documents/Joining%20%28Oct%2003%29.pdf

http://www.specialmetals.com/documents/fabricating.pdf

http://www.specialmetals.com/documents/Product%20Handbook.pdf

Finally, Technical papers:

http://www.specialmetals.com/technical.php

Well, that's about all I could gather for now... If I find anything else of relevance, I'll post it here.

Respectfully,
Henry

P.S. You need to give us much more information in order for any of us to assist you  because after all if i could read your mind, I wouldn't be here wasting my time...
I'd be in the best casino piling up the cash - CAPECHE??? In other words, the most details as possible is necessary for anyone to help you in depth.