Tube S 17 8 Si (austenitische Legierung desTyps FeCrl8Ni8Si4Mn mit 2 18% S-Ferrit) gegen interkristalline Korrosion (IK) wurde mit Hilfe der elektrochemischen potentiodynamischen Reaktivierung (EPR), des Salpetersaure-FluBsaure (SF)-Tests nach ASTM A 262 Practice D sowie metallographisch und mikrostrukturanalytisch (REM, EDX) untersucht. Es wurden mit Schutzgas und open arc geschweiote sowie wsrmebehandelte Proben gepruft. Der SF-Test wurde auaerdem in weniger aggressivenvarianten wie 2 M HN03 + 0,5 M HF. 30°C erprobt. In SF besteht kein direkter Zusammenhang zwischen der relativen Korrosionsgeschwindigkeit und IK-Anfalligkeit , was auf eine Inhibition durch Fe-111-Ionen zuruckgefuhrt wird. Durch freies und potentiostatisches Atzen in SF-Losung konnen jedoch chromverarmte Bereiche und zerfallener 6-Ferrit sichtbar gemacht werden. Mit einem optimierten double-loop-EPR-Verfahren (0,5 M H2S04 + 0,01 M KSCN, 30°C) wurde eine Sensibilisierung iiber das Reaktivierungs/Passivierungs-Ladungsverhaltnis in Verbindung mit einer Gefugebeurteilung ermittelt. Die Ergebnisse zeigen, daB die entwickelte EPR-Variante im Gegensatz zu den konventionellen Verfahren zur IK-Prufung bei bis zu 30% S-Ferrit geeignet ist. In geschweifitem Ausgangszustand (SAZ) sind alle Proben bestandig.Temperaturen von 400 "C bzw. 450 "C werden bis mindestens 1000 bzw. 100 h vertragen. Sensibilisierung kann durch Carbid-und o-Phasenausscheidung sowie durch den Zerfall von 6-Ferrit eintreten, dessen Menge und Verteilung dann entscheidend ist. The corrosion resistance against intergranular attack (IGA) of weld claddings from the electrode Tube S 17 8 Si (alloy type FeCrl8Ni8Si4Mn with 2 18% &ferrite) has been investigated using electrochemical potentiodynamic reactivation (EPR) technique, the nitric-hydrofluoric acid (SF) test according to ASTM A 262 practice D, metallographic and microstructure analytical methods (SEM, EDX). Samples produced by different welding techniques (shielded arc and open arc) and partly additional thermal treated have been investigated.In standardized SF-solution and in 2 M HN03 + 0.05 to 0.5 M HF at 30°C there is no correspondence between corrosion rate and IGA-susceptibility, possibly caused by inhibitive action of Fe-111-ions. SF etchants evaluate Cr-depleted zones and decomposed S-ferrite. In the optimized EPR double loop test in 0.5 M H2S04 + 0.01 M KSCN at 30°C the extend of sensitization is indicated by the ratio of reactivation to passivation charge with additional assessment of the microstructure. It is shown that the EPR-test in the evaluated manner is able to find out IGA at claddings up to 30% &ferrite. In the as-welded state all claddings are resistant. Treatments at 400°C resp. 450°C were tolerated up to at least 1000 resp. 100 h. Sensitization may be caused by precipitation of Cr-rich carbides and by decomposition of &ferrite, for IGA the amount and distribution of ferrite plays a decisive role.

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Panzerungen aus Cobaltbasislegierungen (Stellite) werden vielfach fur den Einsatz unter kombinierter Korrosions-und Verschleifibeanspruchung bei hoheren Temperaturen verwendet. Fur Einbauten in Kernreaktoren sind jedoch cobaltfreie Uberziige erforderlich, um eine moglichst niedrige Strahlenbelastung zu erreichen. Dariiber hinaus besteht aus Kostengriinden ein allgemeines Interesse der Armaturenindustrie an cobaltfreien SchweiBzusatzwerkstoffen. Das Problem bei der Entwicklung cobaltfreier Ersatzlegierungen besteht darin, dal3 diese eine ebenbiirtige VerschleiB-und Korrosionsbestandigkeit aufweisen miissen.Es wurden AuftragschweiRungen der niobhaltigen Fiilldrahtelektrode Stelloy Fe12 mit ca. 19% Cr und 10% Ni hinsichtlich ihrer Bestandigkeit in 0,5 M Schwefelsaure bei 66 "C sowie gegeniiber interkristalliner Korrosion (IK) im Vergleich zur Cobaltbasislegierung Stelloy 6 untersucht.Die im Dauertauchversuch ermittelte Bestandigkeit in Schwefelsaure war nicht zufriedenstellend. Dagegen erwiesen sich beide Elektroden bzw. Auftragschweihngen im EPR-Verfahren als IKbestandig. Nachteilig auf die Beurteilung wirkt sich die hohe Matrixauflosung an geschliffenen Proben aus.Cobalt hard-facing alloys are often used under complex conditions with combined wear and corrosion attack at higher temperatures.For using in equipments of atomic power plants cobalt free claddings are required to guarantee a low radioactivity level. Beside this there is an economic interest of the industry to use cobalt free welding filler metals. The problem consists in developing of cobalt free hard-facing alloys with the same wear and corrosion resistance as cobalt base alloys.The resistance of claddings of the electrode stelloy Fe12 with about 19% Cr and 10% Ni has been investigated in 0.5 M sulfuric acid at 66 "C during a full immersion test in comparison with the cobalt base alloy stelloy 6. Both investigated materials have no satisfactory corrosion resistance. But according to the EPR-test they were resistant against intergranular attack (IK). The high matrix dissolution of grinded samples was disadvantageous to evaluate IK resistance by EPR-test.

The object of this research effort was the investigation, through analytical studies and experimental testing, of several blade-to-disk attachment concepts and airfoil shell-to-strut attachment concepts to determine the optimum concept for use on future small, high-temperature turbine rotors. Appropriate technical personnel of the U.S. Army Aviation Materiel Laboratories have reviewed this report and concur with the conclusions contained herein.The findings and recommendations outlined herein will be taken into consideration in the planning of future axial turbine programs. Task ABSTRACTThis report describes the analytical, experimental, and developmental efforts that were conducted to design, fabricate, test, and evaluate turbine-rotor blade to rotor disk (blade/disk) attachment methods for an air-cooled turbine rotor in a small gas turbine engine. This investigation was launched because the combination of factors that are necessary to satisfy the design requirements of a small cooled gas turbine has made it increasingly difficult to utilize conventional blade attachment means. Specifically, the program was directed toward achieving a suitable attachment method for an axial turbine with an inlet temperature of 2400 0 F, an airflow rate of 4.0 lb/sec, a tip speed of 1500 ft/sec, and matched to a compressor having a 10:1 pressure ratio.Detailed aerothermodynamic design activities were conducted to determine a turbine design that would provide optimum specific fuel consumption (SFC) and specific horsepower (sp hp), The design included an optimization study to obtain the best compromise of turbine efficiency, cooling geometry, blade and disk stress effects, and fabrication considerations.Detailed mechanical design activities were conducted in parallel with fabrication technology development efforts to establish the materials, designs, joining methods, and fabrication techniques necessary to determine feasible means of blade/ disk attachment. Results of these activities showed that diffusion-bonding, brazing, and electron-beam-welding blade/ disk attachment methods possess the greatest potential for application in the subject turbine design.A secondary purpose of the mechanical design and fabrication development activities was to study the feasibility of developing the strut-supported sheet metal blade (shell/strut attachment) that was revealed by the aerodynamic optimization study to be the most effective blade cooling configuration. Full evaluation of the shell/strut attachment was beyond the scope of this program; however, it was determined that both diffusion-bonding and cast-bonding concepts of joining could be considered as feasible methods to develop for the purpose of shell/strut attachment.A final fabrication and test activity was conducted to complete evaluations of the three blade/disk attachment methods. Final specimens were designed, fabricated, inspected, and subjected to tensile,stress-rupture, and low-cycle fatigue testing at 1200 0 F.iii Evaluation of the final specimen test results revealed that (...

The effort reported herein was conducted by the AiResearch Manufacturing Company under the terms of Contract DA 44-177-AMC-183(T), Task 1G162204AO1409. The analytical, experimental, and development efforts that were conducted under the uncooled turbine program are described in the three volumes of the final report. Volume I presents the results of material investigations (both USAAVLABS-and company-sponsored) that were conducted to develop a material that would be suitable for the turbine components of a 2400OF uncooled turbine. Volume IT oresents the results of the aerodynamic, thermodynamic, and mechanical design activities that were conducted for the design of a 2400 0 F uncooled turbine. Volume III presents the results of a test-evaluation program that wzs condurted to determine the feasibility of a fluidic temperature-senzing system for the measurement of TIT's in a 2400OF aas turbine engine. The manager of the Small Gas Turbine Engine Project was Mr. D. G. Furst, and the program manager of this uncooled-turbine program was Mr. F. Weber.