Study on Mechanical and Corrosion Properties of Fe-Mn Alloy for Soluble Ball Seats

In high-temperature and high-pressure corrosion environments, soluble ball seats would fail prematurely due to insufficient strength, hardness and rapid degradation. Therefore, the microstructure and phase composition of the Fe-Mn alloy for soluble ball seat materials were characterized by optical microscope（OM）, scanning electron microscope（SEM）, and X-ray diffraction（XRD）. In addition, the mechanical and corrosion properties of the Fe-Mn alloy were studied by means of electrochemical tests, mechanical property tests, accelerated immersion corrosion tests, and high-temperature and high-pressure immersion corrosion tests. The test results indicated that Mn could refine grains. With the increase of Mn content, the hardness and yield strength of the alloy first increased and then decreased. The hardness and yield strength of Fe-5Mn alloy was 345 HV and 812 MPa, respectively. With the increase in Mn content, the self-corrosion potential changed negatively, and the corrosion current density increased. The self-corrosion current density of Fe-5Mn alloy was 4.64 × 10^-5mA/cm². In the experimental environment of long-term accelerated immersion corrosion, the increase in Mn content led to the decrease of the corrosion rate, and the ultimate degradation rate of Fe-5Mn was 4.3 mm/a. In the long-term high-temperature and high-pressure immersion experiment, the increase in Mn content at the initial stage of corrosion increased the corrosion rate, while the overall corrosion rate of the alloy was slow and tended to be stable at later stages of corrosion. In conclusion, Fe-5Mn met the performance requirements for soluble ball seat materials. This study could provide a reference for the application of Fe-Mn alloy in downhole soluble ball seats.