Materials Design for Corrosion Rate Control in PM AZ91 Mg Alloy by Fe Addition

Abstract

Multi-stage hydraulic fracturing is a well-stimulation or hydrocarbon production enhancement process in which rock formation are fractured within isolated hydrocarbon well zones due to the injection of viscous liquids carrying propane gas. An important piece of hardware in multistage fracturing to create a temporary seal between hydrocarbon producing zones is a so-called a frac ball. Today, frac balls are most often made of reinforced polymers and are therefore greatly limited in pressure and temperature, indirectly restricting the number of stages per well that may be stimulated. As alternate to polymers, magnesium (Mg) and its alloys may be engineered for greater strength at rock formation temperatures, and the normally considered deficiency of magnesium and its alloys such as a limited corrosion resistance may be now advantageously used to create eco-friendly and fully degradable frac balls. Utilizing galvanic corrosion as a general principle to accelerate and control corrosion, magnesium may be used in combination with normally considered transition- metal impurities such as iron (Fe). However, the presence of iron in magnesium and its alloys is also known to influence mechanical properties adversely. Therefore, the relationships between Fe content, corrosion resistance, and mechanical properties still remain to be established for a specific manufacturing and heat treatment process. In this particular study, samples of AZ91 (Mg-9% Al-1% Zn) having various levels of iron were fabricated utilizing spark plasma sintering (SPS). Both compressive properties and corrosion rates were investigated and correlated to iron content.