Japan's largest platform for academic e-journals: J-STAGE is a full text database for reviewed academic papers published by Japanese societies

Friction stir welding (FSW) is a promising joining technique offering safety, repeatability, reduced energy consumption, no need for shielding gases and consumables, and no solidification is involved. To date, extensive efforts have been dedicated toward developing a good combination of friction stir welding process parameters, focusing on tool rotation speed and welding speed to produce sound welds with good corrosion resistance. In this review, we highlight the quantified corrosion resistance performances of reported friction stir welded aluminium alloys under electrochemical testing, which can be used as the benchmark for future studies in this field. A general introduction to friction stir welding technology, heat input formulation and welding temperature, corrosion mechanism and effect of welding parameters are discussed. It is followed by challenges and an outlook toward the practical use of friction stir welding technology.

In an attempt to reduce the oxidation and Cr evaporation rates of solid oxide fuel cells (SOFCs) interconnect, Cu-Fe coating was developed on the AISI 430 ferritic stainless steel substrate by a pulsed current electrodeposition method. Effects of pulse frequency on properties and performance of the fabricated coating were investigated. Results show that Cu-Fe alloy was sucessfully fabricated using pulse deposition methods. The variation of pulsed frequency during pulse current deposition strongly influence the coating morphology and its composition. The increase of pulse frequency tend to increase the Cu-Fe grain size. Moreover, the amount of Cu particles decreases with the increase of pulse frequency.

The surface condenser in the steam turbine plays an essential role during the condensation process. Failure of surface condenser tubes is a critical factor for its efficiency and lifetime. This paper presents the failure of a surface condenser's admiralty brass tubes from a petrochemical plant in Indonesia after four years out of twenty years of expected lifetime. Eddy Current inspection results show some of the leaks were in the condensing zone. The characteristics of ammonia corrosion were found after visual and SEM examinations. Examination using stereo and metallurgical microscopes showed that the tubes' external surface experienced corrosion, grooving attack, and significant wall thinning. SEM observation at the edge of the baffle revealed the preferential attack at the alloy's grain boundaries. Water quality analysis indicated high ammonia concentration because the excess amount of Elimin-Ox oxygen scavenger in the water can produce ammonia that corroded the tubes, leading to leakage and failure.

In this work, the oxidation behavior of Fe-20wt.%Cr alloys with different titanium contents: 0, 0.5, and 1 wt.% are studied as a function of time in air atmosphere. The samples were isothermally oxidized at 700°C for 24, 48, and 96 h in a box furnace. The area specific resistance of oxides formed at the alloys surface during oxidation is measured by four-point probe methods at 700°C for 24 h. For Ti containing alloys, surface morphology observation by SEM shows that a few of TiO₂ particles formed on the top of Cr₂O₃ scales. Continous TiO₂ layer was not formed at the alloys surface after oxidation. XRD analysis on the oxide scales of Fe-20Cr-Ti alloys confirms that Cr₂O₃ and TiO₂ oxide formed on the alloys. Ti addition into the alloys increases the oxidation rates of alloys at the initial stages. Oxidation behavior of Fe-20Cr-0.5Ti and Fe-20Cr-1Ti alloys showed two regimes. The parabolic rate constant, k_p (in gr²/cm⁴s) were 1.57 x 10^-13 and 3.08 x 10^-13 respectively for initial stage of oxidation then changed to-9 x 10^-15 and-3 x 10^-14 respectively for the remainder of the test. ASR measurement shows that the presence of Ti in the alloys decreases the electrical resistance up to 60%. Ti addition into Fe-Cr alloys affect the oxide growth rate and increase the conductivity of Cr₂O₃ scales.