As stated above. The benchmark currently accepted by most fabricators and depot level repair stations for aerospace fusion welding is Mil Std 1595A, However AWS has published D17.1 in 2001, my understanding is that the new AWS standard was/is intended to superseed/replace 1595. I have reviewed it and it appears comprehensive and up to date, especially in dealing with titanium post weld surface conditions. D17 addresses certification/qualification standards, filler selection and Visual/destructive examination of test welds. It includes catagories of criticality. The best part is that it is mercifully brief, comming in at about 100 pages.