Volume 23, Issue 60, July - December, 2026

Multi-Objective Optimization of Nitriding Factors for SPS-Ti–Al–Zr Alloy utilizing Grey Relational Analysis

Ekhlas K. Zamel^1♦, Haydar Al-Ethari¹, Ali H. Haleem¹

¹Metallurgical Engineering Department, College of Materials Engineering, University of Babylon, Babylon 51001, Iraq

^♦Corresponding Author
Ekhlas K. Zamel, Metallurgical Engineering Department, College of Materials Engineering, University of Babylon, Babylon 51001, Iraq

ABSTRACT

To support the long-term performance of load-bearing orthopedic implants, candidate materials should exhibit high surface hardness, excellent corrosion resistance, enhanced wear resistance, and adequate biocompatibility. In this study, a titanium–aluminum–zirconium (Ti–2Al–2.5Zr) alloy was fabricated by Spark Plasma Sintering (SPS) and subsequently treated by gas nitriding to improve its surface characteristics. Surface modification was carried out by gas nitriding method which is based on the diffusion of nitrogen atoms into the metallic lattice, thus forming a dense nitride layer, which improves hardness, corrosion resistance and wear properties. The effects of nitriding temperature, processing time and gas flow rate on surface hardness, corrosion rate and wear behavior were systematically investigated using Taguchi’s L9 orthogonal array. The results confirmed the formation of a thin, dense and adherent nitride layer composed mainly of TiN and Ti2N, integrated with the porous SPS microstructure. This layer increased surface hardness to 704–1016 Hv reduced corrosion rate to 0.211–4.09 mpy, and improved wear resistance to 5.7×10⁻⁹– 7.5×10⁻⁹ g/cm³. Grey Relational Analysis (GR) identified 1050 °C, 35 min, and 15 cm³/min as the optimum nitriding conditions, while ANOVA showed that nitriding temperature was the most influential factor.

Keywords: Ti–Al–Zr alloy, Spark Plasma Sintering (SPS), Nitriding, Surface hardness, and Orthopedic implants

Indian Journal of Engineering, 2026, 23(60), e17ije1722

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Published: 18 October 2026