Effect of Ti addition on microstructure and mechanical properties of Co-Cr-Mo alloy developed by µ-plasma arc metal powder additive manufacturing process

Balbir Singh Negi; Pradyumn Kumar Arya; Neelesh Kumar Jain; Sharad Gupta; Ankur Srivastava

doi:10.1038/s41598-026-35741-w

Effect of Ti addition on microstructure and mechanical properties of Co-Cr-Mo alloy developed by µ-plasma arc metal powder additive manufacturing process

Sci Rep. 2026 Feb 4;16(1):7308. doi: 10.1038/s41598-026-35741-w.

Authors

Balbir Singh Negi¹, Pradyumn Kumar Arya², Neelesh Kumar Jain³, Sharad Gupta⁴, Ankur Srivastava⁵

Affiliations

¹ Department of Mechanical Engineering, Indian Institute of Technology Indore, Indore, Madhya Pradesh, 453552, India.
² Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, 110016, India.
³ Department of Mechanical Engineering, Indian Institute of Technology Indore, Indore, Madhya Pradesh, 453552, India. nkjain@iiti.ac.in.
⁴ Department of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, Indore, Madhya Pradesh, 453552, India.
⁵ Department of Mechanical Engineering, Manipal University Jaipur, Jaipur, 303007, India. ankur.srivastava@jaipur.manipal.edu.

Abstract

This paper presents effects of addition of 4wt.% of Ti to Co-Cr-Mo alloy by µ-plasma arc metal powder additive manufacturing (µ-PAMPAM) process on microstructure, phase evolution, bending strength, tensile and compressive yield and ultimate strength, % elongation, microhardness, porosity, and density of the resultant alloy and their comparison with Co-Cr-Mo alloy. Microstructure and phase evolution study of Co-Cr-Mo alloy showed Co-rich matrix comprising of γ-Co and ε-Co phases, formation of Cr₇C₃ and Cr₂₃C₆ carbides due to presence of carbon and affinity of Cr towards it, and micro-cracks. Addition of 4 wt% Ti to Co-Cr-Mo alloy refined its grains, minimized formation of micro-cracks, led to formation of β-Ti phase and Co-Ti intermetallic compound along with the chromium carbides. It also reduced porosity and density of the resultant Co-Cr-Mo-4Ti alloy. Grain refinement increased flexural strength of Co-Cr-Mo-4Ti alloy. Solid solution effect of Ti increased tensile and compressive yield strength, ultimate compressive and tensile strength, and percentage elongation of Co-Cr-Mo-4Ti alloy as compared to Co-Cr-Mo alloy. Microhardness of Co-Cr-Mo-4Ti alloy increased to 473 MPa from 382 MPa of Co-Cr-Mo alloy due to formation of Co-Ti intermetallic compound and β-Ti phase. All these improvements enhance durability and strength of Co-Cr-Mo-4Ti alloy along with a reduction in stress shielding effect as compared to the Co-Cr-Mo, making it more suitable for knee prothesis applications.

Keywords: Co–Cr–Mo alloy; Co–Cr–Mo–4Ti alloy; Multilayer deposition; Ti addition; µ-PAMPAM process; Β–Ti.