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Solid-particle erosion of aluminum/particulate ceramic composites

Description: Impact erosion of 2014 aluminum, 2014 aluminum + 20 vol % particulate silicon carbide, and 2014 aluminum + 20 vol % particulate aluminum oxide has been studied at room temperature. The alloys were tested in the as-received and heat-treated conditions. Experiments were conducted with aluminum oxide abrasive in vacuum in a slinger-type apparatus over a range of abrasive size, velocity, and angle of impact. Erosion rates were influenced by reinforcement and heat treatment. Reduced ductility, both overall and local, attributed to reinforcement or heat treatment, caused, under most conditions, more rapid erosion of the composites. The data suggest that erosion rate can be minimized by proper microstructural control, involving reducing reinforcement segregation and the amount of intermetallic compounds. 37 refs., 7 figs.
Date: June 1, 1990
Creator: Goretta, K.C.; Wu, W.; Routbort, J.L. (Argonne National Lab., IL (USA)) & Rohatgi, P.K. (Wisconsin Univ., Milwaukee, WI (USA))
Partner: UNT Libraries Government Documents Department

Elastic and plastic strains and the stress corrosion cracking of austenitic stainless steels. Progress report, April 30, 1977--December 30, 1977

Description: A newly developed test environment based on NaCl, Na/sub 2/SO/sub 4/, and HCl has provided some insight to several aspects of SCC in a transformable austenitic stainless steel. Current vs. time curves indicated the presence of the formation of a ''protective'' film which drastically reduced the anodic current leading to failure. This film, not indicated by the polarization curves, is subject to highly localized damage such as pitting. Thus, although it allows only very small corrosion currents, it is not truly protective. Hence, it is pseudo-passive. The critical cracking potential did not exhibit any difference between the annealed and the maximum (25%) deformation examined. The corrosion or open circuit potential for both annealed and deformed material behaved in a similar manner, becoming more noble with time until it reached the critical cracking potential and SCC ensured. The failure time for the deformed specimens was substantially shorter than for the annealed ones, but the incubation time was essentially the same. Within the range of experimental conditions examined thus far, it appears that the critical parameters leading to SCC in a chloride environment are primarily dependent on surface-environment interactions and not dependent on the bulk properties.
Date: January 1, 1978
Creator: Troiano, A.R.
Partner: UNT Libraries Government Documents Department

Elastic and plastic strains and the stress corrosion cracking of austenitic stainless steels. Final report

Description: The influence of elastic (stress) and plastic (cold work) strains on the stress corrosion cracking of a transformable austenitic stainless steel was studied in several aqueous chloride environments. Initial polarization behavior was active for all deformation conditions as well as for the annealed state. Visual observation, potential-time, and current-time curves indicated the development of a pseudo-passive (flawed) film leading to localized corrosion, occluded cells and SCC. SCC did not initiate during active corrosion regardless of the state of strain unless severe low temperature deformation produced a high percentage of martensite. Both elastic and plastic deformation increased the sensitivity to SCC when examined on the basis of percent yield strength. The corrosion potential, the critical cracking potential, and the potential at which the current changes from anodic to cathodic were essentially unaffected by deformation. It is apparent that the basic electrochemical parameters are independent of the bulk properties of the alloy and totally controlled by surface phenomena.
Date: August 1, 1979
Creator: Vaccaro, F.P.; Hehemann, R.F. & Troiano, A.R.
Partner: UNT Libraries Government Documents Department

Burst testing of alloys 800 and 310 at 1,255 K (1,800/sup 0/F) with a simulated coal gasification atmosphere

Description: Several corrosion- and heat-resistant alloys are being considered for long term applications in coal gasification plants at temperatures up to 1.255/sup 0/K in high pressure environments of mixed hydrogen, water, hydrocarbons, and sulfides. A method for in situ testing has been developed for short time mechanical tests of candidate alloys in high pressure, high temperature, gaseous environments, referred to as coal gasification atmosphere (CGA). The method involves bursting thin-walled tubes, using various gases to produce the burst hoop stress. The short time 1.255/sup 0/K burst and creep rupture strength and ductility properties of alloys 800 and 800H in a mixed gas environment, H/sub 2/, CO, CO/sub 2/, CH/sub 4/, SO/sub 2/ (CGA), are not reduced from properties obtained in air. However, the stress- and pressure-accelerated corrosion is more severe in CGA. It is expected that CGA will reduce long term strength and ductility in alloy 800 as a result of the accelerated corrosion. The short time 1.255/sup 0/K strengths of alloy 310 in CGA and pure hydrogen environments are reduced from the values obtained in air by less than 10 percent. The ductilities (total circumferential elongation) are good--approximately 20 percent for all test conditions. The CGA stress- and pressure-accelerated corrosion is greater than in air. Longer time tests in CGA are expected to result in additional strength degradation. Limited creep/fatigue tests of alloy 310 in hydrogen show that hold times are significant. A greater cyclic life is observed using an 8-second hold time than a 55-second hold time.
Date: May 1, 1976
Creator: Dixon, C. E.
Partner: UNT Libraries Government Documents Department