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The high-strength Al-Zn-Mg-Cu alloy (AA7050) used in manufacturing of main landing gear links in aerospace application and found to have failures in its application due to deterioration in material property (wear and SCC). In this work, an attempt was made to replace AA7050 with AA7050 hybrid composite material fabricated through stir casting. The AA7050/B4Cp/SiCp hybrid composites were prepared with 7.5 wt.% boron carbide particles added with 2.5, 5, 7.5 and 10 wt.% of silicon carbide. Addition of potassium titanium fluoride (K2TiF6) flux improved the bonding of matrix and reinforcement due to the titanium interface. The effect of percentage reinforcement on mechanical wear and sulphide stress corrosion cracking (SSCC) were analysed. The composite with 2.5% of silicon carbide offers better resistance to wear. The stress corrosion and wear mechanisms were studied with the aid of scanning electron microscopy. The hybrid composite showed enhancement in tensile strength owing to the clear bonding of matrix and the reinforcements. The reinforced composites showed improvement in SSCC due to grain boundary precipitates. [ABSTRACT FROM AUTHOR]

The electrochemical and sulfide stress corrosion cracking (SSCC) behaviors of 13Cr stainless steel and P110 steel were investigated in a simulated acidic annular environment with low-temperature and high-pressure HS/CO using electrochemical methods, U-bend immersion tests, and scanning electron microscopy. In the solution containing high pressure CO, 13Cr, and P110 steels exhibited general corrosion and severe pitting, respectively. Compared with sweet corrosion, additional HS in the solution enhanced the corrosion of 13Cr steel but inhibited the corrosion of P110 steel. By contrast, in a solution containing 4 MPa CO and different $$ {P}_{{{\text{H}}_{ 2} {\text{S}}}}$$ (0-0.3 MPa), the susceptibility of both 13Cr stainless steel and P110 steel toward SSCC was significantly promoted by increases in HS partial pressure. The 13Cr stainless steel exhibited higher susceptibility toward SSCC than P110 steel under a HS/CO environment but lower susceptibility under a pure CO environment. [ABSTRACT FROM AUTHOR]

The susceptibility to sulphide stress corrosion cracking (SSCC) of four conditions of shielded metal arc welding repairs and one as welded specimen of the girth weld in seamless API X-52 microalloyed steel pipe were evaluated using slow strain rate tests. The slow strain rate tests were performed in air and in a NACE solution saturated with H2S both at room temperature to a constant elongation rate of 25·4 × 10–6 mm s–1. The SSCC susceptibility was evaluated in function of the reduction in area ratio and elongation ratio and also was manifested as a decrease in the mechanical properties. According to this consideration it is clear that all the weldments exhibit a great susceptibility to SSCC. After failure, the fracture surfaces were observed in the scanning electron microscope. The metallographic observations of the fractured specimens showed that the most susceptible area to SSCC was the intercritical heat affected zone. [ABSTRACT FROM AUTHOR]