Evaluation of residual stresses induced by cold spraying of Ti-6Al-4V on Ti-6Al-4V substrates

Dibakor Boruah, Bilal Ahmad, Tung Lik Lee, Saurabh Kabra, Abdul Syed, Philip McNutt, Matthew Doré, Xiang Zhang

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4 Citations (Scopus)

Abstract

Cold spray (CS) is a solid-state additive material deposition technique, which has gained attention in the aerospace industry as a potentially viable technology for structural repair of high-value parts made of high-strength alloys such as Ti-6Al-4V (Ti-64). Residual stresses build up in the substrate and deposited materials resulting from the CS process can influence the integrity of a coating or repair. However, the nature, magnitude and distribution of residual stresses in Ti-64/Ti-64 CS repairs are currently unknown. This study aims to evaluate the effects of geometrical variables (i.e. the number of CS layers, CS layer thickness, and substrate thickness) and track pattern on the magnitude and distribution of residual stresses in CS deposit-substrate assemblies. Through-thickness stress distributions were measured experimentally by neutron diffraction and contour method. Furthermore, a comparison among different residual stress build-up mechanisms induced by CS processes has been discussed for different combinations of substrate and deposit assemblies. An analytical model based on the force and moment equilibrium requirements was used to interpret the experimental stress profiles and to predict the residual stress distribution. It was found that residual stresses are highly tensile near the free surface of the Ti-64 deposits as well as towards the bottom of the substrate, and compressive near the interface region. Although all the specimens showed similar stress distribution, the magnitudes were found to be higher in one or more of the following cases: specimens with a higher number of CS layers, lower substrate thickness, higher layer thickness (i.e. at lower scanning speed), and deposited with a horizontal track pattern.
Original languageEnglish
Pages (from-to)591-602
Number of pages12
JournalSurface and Coatings Technology
Volume374
Early online date11 Jun 2019
DOIs
Publication statusPublished - 25 Sep 2019

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Bibliographical note

NOTICE: this is the author’s version of a work that was accepted for publication in Surface and Coatings Technology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Surface and Coatings Technology, [374], (2019) DOI: 10.1016/j.surfcoat.2019.06.028

© 2019, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/

Funder

Lloyd's Register Foundation

Keywords

  • Additive manufacturing
  • Cold spray
  • Residual stress
  • Coatings
  • Repairs
  • Thermal spray
  • Ti-6Al-4V
  • Neutron diffraction
  • Contour method
  • Titanium alloys
  • Remanufacturing
  • Ti6Al4V titanium alloy
  • Ti-64

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