In the realm of high-performance materials, the nickel-based superalloys Inconel X750 and Inconel 718 have carved out unique positions due to their exceptional characteristics. They are renowned for their superior high-temperature strength, corrosion resistance, and precipitation hardening capabilities. These features make them fundamentally distinct from solid solution alloys. In this comprehensive guide, we delve into a detailed comparison between these two alloys, analyzing their history, chemical composition, properties, and applications.
Table of Contents
Introduction
Inconel X750 and Inconel 718 belong to the family of nickel-chromium-based superalloys. They are renowned for their high-temperature strength and excellent corrosion resistance. These superalloys are commonly used in applications that require durability and stability in extreme environments.
History of Inconel X750 and 718
The Inconel alloys were developed in the 1950s and 1960s by the US-based Specialty Metals Corporation. The Inconel 718 (UNS N07718) and Inconel X750 (UNS N07750) are among the most well-known members of the Inconel family.
Chemical Composition
Both Inconel 718 and Inconel X750 are comprised primarily of nickel, chromium, and iron. However, Inconel 718 has stricter controls over harmful elements. The presence of molybdenum in Inconel 718 enhances its durability at high temperatures, making it superior to Inconel X750 in this aspect.
Heat Treatment
Inconel 718 can be heat treated to achieve higher strength levels, while maintaining excellent corrosion resistance and good formability characteristics. On the other hand, heat treating is not recommended for Inconel X750 due to its low thermal conductivity, making it difficult to achieve uniformity during heat treating operations.
Tensile Properties
In terms of tensile properties, Inconel 718 has a higher ultimate tensile strength (UTS) than X750 at room temperature. This makes Inconel 718 more suitable for high-strength applications such as turbine blades and fasteners.
Corrosion Resistance
Inconel 718 surpasses Inconel X750 in corrosion resistance due to its higher chromium content. Additionally, the inclusion of molybdenum in Inconel 718 enhances its resistance to pitting and crack corrosion.
High Temperature Strength
Inconel 718 exhibits superior high-temperature strength compared to Inconel X750. The addition of molybdenum, an ideal solid solution strengthening element, increases the base strength of the alloy.
Melting Point
Although Inconel 718 has better high-temperature strength, its melting point is lower than that of Inconel X750. This is primarily due to Inconel 718’s higher iron content, which has a lower melting point than nickel.
Applications
Both Inconel 718 and Inconel X750 are extensively used in aerospace engine applications. However, due to its superior corrosion resistance, Inconel 718 is also widely utilized in the oil and gas, petroleum processing, and power generation sectors.
Price Considerations
While Inconel 718 outperforms Inconel X750 in most aspects, the price difference between the two is not substantial. This is primarily because Inconel 718 contains less nickel and more iron, reducing the raw material cost of the alloy.
Conclusion
In summary, Inconel 718 offers better performance than Inconel X750 in terms of high-temperature strength, corrosion resistance, and a wider range of applications. Therefore, Inconel 718 is a superior superalloy from both performance and cost perspectives.
