Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 30123
Dependence of Densification, Hardness and Wear Behaviors of Ti6Al4V Powders on Sintering Temperature

Authors: Adewale O. Adegbenjo, Elsie Nsiah-Baafi, Mxolisi B. Shongwe, Mercy Ramakokovhu, Peter A. Olubambi

Abstract:

The sintering step in powder metallurgy (P/M) processes is very sensitive as it determines to a large extent the properties of the final component produced. Spark plasma sintering over the past decade has been extensively used in consolidating a wide range of materials including metallic alloy powders. This novel, non-conventional sintering method has proven to be advantageous offering full densification of materials, high heating rates, low sintering temperatures, and short sintering cycles over conventional sintering methods. Ti6Al4V has been adjudged the most widely used α+β alloy due to its impressive mechanical performance in service environments, especially in the aerospace and automobile industries being a light metal alloy with the capacity for fuel efficiency needed in these industries. The P/M route has been a promising method for the fabrication of parts made from Ti6Al4V alloy due to its cost and material loss reductions and the ability to produce near net and intricate shapes. However, the use of this alloy has been largely limited owing to its relatively poor hardness and wear properties. The effect of sintering temperature on the densification, hardness, and wear behaviors of spark plasma sintered Ti6Al4V powders was investigated in this present study. Sintering of the alloy powders was performed in the 650–850°C temperature range at a constant heating rate, applied pressure and holding time of 100°C/min, 50 MPa and 5 min, respectively. Density measurements were carried out according to Archimedes’ principle and microhardness tests were performed on sectioned as-polished surfaces at a load of 100gf and dwell time of 15 s. Dry sliding wear tests were performed at varied sliding loads of 5, 15, 25 and 35 N using the ball-on-disc tribometer configuration with WC as the counterface material. Microstructural characterization of the sintered samples and wear tracks were carried out using SEM and EDX techniques. The density and hardness characteristics of sintered samples increased with increasing sintering temperature. Near full densification (99.6% of the theoretical density) and Vickers’ micro-indentation hardness of 360 HV were attained at 850°C. The coefficient of friction (COF) and wear depth improved significantly with increased sintering temperature under all the loading conditions examined, except at 25 N indicating better mechanical properties at high sintering temperatures. Worn surface analyses showed the wear mechanism was a synergy of adhesive and abrasive wears, although the former was prevalent.

Keywords: Hardness, powder metallurgy, Spark plasma sintering, wear.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1124629

Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 911

References:


[1] C. Veiga, J. P. Davim and A. J. R. Loureiro, “Properties and applications of titanium alloys: a brief review,” Rev. Adv. Mater. Sci. vol. 32, pp. 133–148, May 2012.
[2] A. Mishra, “Analysis of friction and wear of titanium alloys,” Int. J. Mech. Eng. & Rob. Res. vol. 3, no. 3, pp. 570–573, July 2014.
[3] Y. Long, H. Zang, T. Wang, X. Huang, Y. Li, J. Wu and H. Chen, “High-strength Ti-6Al-4V with ultrafine-grained structure fabricated by high energy ball milling and spark plasma sintering,” Materials Science & Engineering A vol. 585, pp. 408–414, July 2013.
[4] Z. Zhaohui, W. Fuchi, W. Lin, L. Shukui and S. Osamu, “Sintering mechanism of large-scale ultrafine-grained copper prepared by SPS method,” Materials Letters vol. 62, pp. 3987–3990, September 2008.
[5] S. Diouf and A. Molinari, “Densification mechanisms in spark plasma sintering: effect of particle size and pressure,” Powder Technology vol. 221, pp. 220–227, January 2012.
[6] A. Teber, F. Schoenstein, F. Têtard, M. Abdellaoui and N. Jouini, “Effect of SPS process sintering on the microstructure and mechanical properties of nanocrystalline TiC for tools application,” Int. Journal of Refractory Metals and Hard Materials vol. 30, pp. 64–70, January 2012.
[7] E. Ergül, H. Özkan Gülsoy and V. Günay, “Effect of sintering parameters on mechanical properties of injection moulded Ti-6Al-4V alloys,” Powder Metallurgy vol. 52, no. 1, pp. 65–71, March 2009.
[8] M. L. Lepule, B. A. Obadele, A. Andrews and P. A. Olubambi, “Corrosion and wear bahaviour of ZrO2 modified NiTi coatings on AISI 316 stainless steel,” Surface & Coatings Technology. vol. 261, pp. 21–27, December 2014.
[9] S. R. Chauhan and Kali Dass, “Dry sliding wear behaviour of titanium (Grade 5) alloy by using response surface methodology,” Advances in Ttribology vol. 2013, pp. 1–9, June 2013.
[10] B. A. Obadele, A. Andrews, P. A. Olubambi, M. T. Mathew and S. Pityana, “Effect of ZrO2 addition on the dry sliding wear behaviour of laser clad Ti6Al4V alloy,” Wear vol. 328-329, pp. 295–300, March 2015.