Enhancing characteristics of hypoeutectic, congruent, and eutectic nickel silicide alloys by optimizing inductively coupled plasma spheroidization parameters for additive manufacturing

Abstract

Nickel-silicon (Ni–Si) alloys are known for their excellent physicochemical, thermal, and mechanical properties, making them suitable for high-temperature oxidation-resistant, corrosion-resistant, and wear-resistant applications. However, their inherent brittleness and the processing challenges associated with conventional methods, such as casting, forging, and machining, limit broader industrial applicability. To address these limitations and enhance their suitability for additive manufacturing (AM), this study investigates the spheroidization of Ni–Si alloy powders using inductively coupled plasma spheroidization (ICPS). The work focuses on hypoeutectic Ni-16.1Si, congruent Ni-32.4Si, and eutectic Ni-38Si (weight%) powders, which initially exhibit irregular morphology and consist of γ-Ni₃₁Si₁₂/δ-Ni₂Si, Ni₃Si₂/NiSi/NiSi₂, and NiSi/NiSi₂ phases, respectively. The ICPS process was optimized by evaluating the effects of plasma power, chamber pressure, and powder feed rate, resulting in the formation of spherical particles with smooth surfaces, narrower particle size distributions, refined microstructures, modified phase compositions, and enhanced flowability, characteristics well-suited for AM requirements. The spheroidized powders were deposited onto S355 steel substrates using a laser-based directed energy deposition process to assess their suitability for surface engineering applications. While higher Si-content alloys exhibited increased susceptibility to microcracking due to residual stress and brittle phase formation, Ni-16.1Si demonstrated the most favorable mechanical performance, including high surface hardness, low abrasion-induced volume loss, and strong resistance to indentation-induced cracking. Overall, this study establishes a strong foundation for the use of spheroidized Ni–Si powders in AM, particularly for applications requiring durable hard surface engineering materials.