Metarinka,
first of all, please let me take this response as the opportunity to thank all the great colleagues who have so kindly replied upon my post!
I am blessed by having you all as fellows aside!
Secondly, I would like of course to try to give a brief about the nature and discussions of the conference.
Basically it was the eighth conference been organized and held by the EPRI and as they said, it is a continuously growth recognizable over the last years. This conference was attended by 360(!) experts from all over the world. Oh, please forgive me... 359 experts + myself :-).
Two sessions were held parallel one to another, Nuclear and Fossil. I have attended - with the exception of two presentations - the "Nuclear" session. But as much as I have enjoyed to participate in this session the much I have regret to not having been able to attend the "Fossil" session, since there were excellent papers as well presented. The only presentations in the "Fossil" session I have listened to came from MATSUI and RAGHUNATHAN. MATSUI from Mitsubishi Heavy Industries dealt with the weld overlay of a caloric power station boiler component ("water wall") under using Alloy 622 filler wire. He presented the investigations which led to the final application as the long-term and failure examination results. The second one came from RAGHUNATHAN from TWI Cambridge dealing with Novel Technologies for Repair and Refurbishments in the Power Industry and Case Studies. Very interesting at all.
The "Nuclear" session could be roughly distinguished over the two days I have attended.
The first day was characterized by presentations dealing particularly with metallurgical questions with the very special base and filler metals used in the nuclear industry.
I can remember so well the presentations coming from Prof. Lippold (THE Ohio State University) and Prof. DuPont (Lehigh University) - oh dear the names alone!
Lippold gave two lectures. The first dealt with the investigations to improve the Ductility Dip Cracking (DDC) resistance of filler metal Alloy 52 or 52M. There were some cracking problems observable in the past with these variants and Lippold et al have developed an alloy composition containing 2.5 wt% Nb as 4.0 wt% Mo to increase the critical strain resistance by the factor of 4. Whereas Alloy 52(M) has a critical strain of ~ 2% to initiate first DDC, Alloy 52X-H (so the experimental alloy designation) could be strained by >8% before the first cracks were indicated. By the way, even this experimental composition is already being used meanwhile by the "Special Metals" company and will be commercially available short-term by the trade "Inconel 52MM".
The second lecture from Lippold dealt with the development of IN 52M Overlay for surge nozzle weld repairs. A real practical damage of a surge nozzle was investigated and Lippold and his team have found a way to optimal repair even this damaged component by combining a first layer of AISI 308L buffering with subsequent overlaying with Alloy 52M.
Prof. DuPont whereas held a lecture on welding Gadolinium (Gd) alloyed base metals for manufacturing spent fuel transportation canisters. Gd has the highest absorption rate for fast neutrons and was thus chosen for even alloying the Ni-Base parent material. However, Gd has strong negative effects on the precipitation of complex and brittle phases deteriorating the mechanical properties of the component welded. Nonetheless DuPont and his team have found a way to process the material by defining the optimal range of alloying composition, precipitation kinetics and weldability.
Some further very interesting presentations treating the improvements in developing filler materials under considering the particular aspects and requirements of the nuclear power industry were given.
Also an interesting presentation about using the X-Ray Diffraction method for measuring residual stresses as two presentations of using a process (Underwater Laser Peening) to even mitigate residual stresses as a pre-emptive measure to avoid Stress Corrosion Cracking were held on the first day.
The second day was more characterized by presentations dealing with "Weld Overlaying" as the nuclear people name it. By the way, I can remember very well the discussion in the forum, at that time initiated by js55 and greatly participated by CWI555, dealing with a clarification of technical terminology in the "surfacing" field.
Well, some very particular papers were treated on weld overlay applications and the continuous try to improve handling and quality of even those operations. I was astonished on the tremendous width of different rudiments to weld overlay in the nuclear field and the enormous variety of base and filler metal compositions.
Above the improvement of weld quality another great topic was treated. The increase of efficiency of the weld processes used.
Some very interesting results were shown by using Tandem Wire GTAW doubling the weld deposition rates by holding the weld quality constantly high. However, even though the modern GMAW processes were, and still are, investigated, everything - so far my humble opinion - is still focused upon GTAW which is highly approved as being capable to meeting the highest requirements of the industry. As far as I estimate, the use of GTAW might be as well the medium- or even long-term future and thus the conference has indirectly approved what already has been stated here within the AWS forum a time ago as we have discussed what future GMAW might have within the nuclear power industry by being accepted as an alternative to GTAW.
Well, as you can see. All in all the conference was an enjoyment for me to attend and a certainly unforgettable experience for me as a welder. It is 100% recommendable to visit and participate in the conference and it was worth every cent to having been there.
Before I forget, the conference organization and conduction was outstandingly as well and even here I bow my head before the US-American fellows who were responsible for accomplishing this project.
But the most impressive for me is and remains - and here I would like to quote Jeff (js55) - that I "have rubbed my elbows with much of the brilliance of the industry" over the three days I have been your guest in Florida!
Therefore once again thanks to you all as you are great and excellent representatives of the USA!
Stephan
EDIT: Just forgotten to add somewhat important for all of you who are waiting for some most interesting bedtime reading.
As Prof. Lippold has mentioned there is a new book to be awaited in fall this year. The authors are Lippold, DuPont et al, and the title will be:
"Welding Metallurgy and Weldability of Nickel Base Alloys" and it will be published with WILEY Interscience!
