Microstructure, mechanical and corrosion properties of 42Sn-(57.5-x)Bi- 0.5Cu-xSb alloys used as permanent plugging materials for the oil and gas extraction

Conventional Sn-Bi alloys often exhibit inferior mechanical properties due to the presence of coarse Bi-rich phase, rendering them susceptible to failure under high-temperature, high-pressure, and corrosive conditions. To address this issue, Sb element was introduced into a 42Sn-57.5Bi-0.5Cu alloy to systematically investigate its effects on microstructure, mechanical properties, and corrosion behaviors. The results indicated that Sb was dissolved in both the Bi-rich phase and β-Sn phase, and the SnSb phase with a size range of 298∼493 nm could be formed at their phase interfaces. When the Sb content was ≤1.5 wt.%, these SnSb phase particles effectively suppressed the coarsening of Bi-rich phase and Cu 6 Sn 5 phase. Consequently, the 42Sn-56Bi-0.5Cu-1.5Sb alloy exhibited an improved elongation of 71.76% and an enhanced compressive strength of 85.39 MPa at 50% strain. Although Sb addition reduced the potential difference between the phases in the alloy, the corrosion rate increased with increasing Sb content, as the formation of the SnSb phase introduced additional micro-galvanic couples. The value was only 0.094 mm/a for the 42Sn-55.5Bi-0.5Cu-1.5Sb alloy, which can still meet the requirements used in the harsh oil and gas well environments. This study provides a novel material for realizing permanent plugging in the field of oil and gas extraction.