Abstract. This paper reports the influence of Mo and Ni on the tensile properties of the modified 13Cr martensitic stainless steels in tempered condition. Four steels with different content of Mo and Ni were prepared by induction melting followed by hot forging, quenching and tempering. The experimental results showed that the addition of about 1% and 3% Mo has a beneficial effect to increase both the tensile strength and the elongation of the steels. On the contrary, the addition of about 3% Ni into the martensitic stainless steel results in decreasing of both the tensile strength and the elongation. Among the alloys investigated the 13Cr3Mo type steel exhibited largest tensile strength of 1348 MPa and largest elongation of 12%. The observation on the tensile fractured surfaces by using scanning electron microscope supported these findings.

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The present paper reports the interdiffusion of Re, W, Ru and Co in the binary and pseudo-binary Ni based alloys at 1523 K and the 0 phase coarsening kinetics of model superalloys at 1324 K. Both Re and W concentration gradients caused Ru uphill diffusion in the respective pseudo-binary diffusion couple, whereas Ru concentration gradient promoted uphill diffusion for W but not for Re. Interestingly, Re uphill diffusion occurred under the influence of Co concentration gradient but the reverse effect was not observed. The cross interdiffusion coefficients qualitatively determined from the uphill diffusion profiles were in reasonable agreement with those reported previously. Comparison of the interdiffusion coefficients in the binary and the pseudo-binary diffusion couples showed that Ru and W decreased the diffusivity of each other whereas Co appeared to be more powerful barrier atoms than Ru to decrease the Re diffusivity. Furthermore, it was evident that the coarsening kinetics of the 0 phase in both Ru-free and Ru-containing model superalloys were controlled by diffusion and Ru was found to have no effect on the rate constant of the 0 phase coarsening.

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The activation enthalpies and frequency factors for interdiffussion of Al and Re in the -phase of Ni-Al-Re ternary system were estimated by a series of experiments using diffusion couples in the temperature range from 1200 to 1300 C. The method developed by Whittle and Green was applied to obtain the interdiffusion coefficients of the solutes (Al, Re) in the system. The activation enthalpies Q and the frequency factors D D o obtained from the experiments confirmed the slower diffusion of Re than Al. In addition, it was found that the influence of Re on the diffusion of Al in the -phase of Ni-Al-Re system was insignificant.

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The diffusion of Re and Ru in the 0 -Ni 3 Al phase has been investigated at a range of temperatures 1423-1523 K by using the pseudo-binary diffusion couples. It was found that the concentration gradient of Re appeared to promote the uphill diffusion of Al, whereas that of Ru did not promote the Al uphill diffusion. The cross interdiffusion coefficients ofD D Ni AlRe andD D Ni AlRu were independent of the matrix ordering since they were comparable qualitatively between those in the 0 -Ni 3 Al and in the -Ni phases. The tracer diffusion coefficients for Re and Ru in Ni 3 Al were estimated by extrapolation and the obtained activation energies were consistent with the site preferences of the elements reported in the literature. Further, the results of this work suggest that the diffusion of Ru in Ni 3 Al is mostly governed by the diffusion in Ni sublattice and the diffusion of Re is mainly controlled by the formation of anti-site defects in the Ni sublattice with negligible contribution of the anti-site bridge mechanism.

Influence of high temperature on corrosion behavior of 304 stainless steel in chloride solutions AIP Advances 6, 115301 (2016) , Efendi Mabruri Abstract. The AISI Type 420 stainless steels are commonly used to steam generators, mixer blades, etc. These stainless steels are most prone to pitting in dissolved Cl -containing environments. In this paper, the effect of tempering temperature on pitting corrosion resistance of AISI Type 420 stainless steels was studied. The AISI Type 420 stainless steels specimens were heat treated at the temperature of 1050°C for 1 hour to reach austenite stabilization and then quench in the oil. After that, the specimens were tempered at the temperature of 150, 250, 350 and 450°C for 30 minutes and then air cooled to the room temperature. The electrochemical potentiodynamic polarization test was conducted at 3.5% sodium chloride solution to evaluate corrosion rate and pitting corrosion behaviour. The Scanning Electron Microscope (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) were used to evaluate the pitting corrosion product. The result have shown that highest pitting potential was found in the sample tempered at 250°C and corrosion pits were found to initiate preferentially around chromium carbides.