Improving titanium friction and wear properties

July 15, 2014

Solar Atmospheres, Souderton, Pennsylvania, USA, has reported that it recently worked with Oak Ridge National Lab, USA, on research focussed on improving titanium friction and wear properties. The experiment, published as “Surface Engineering to Improve the Durability and Lubricity of Ti–6Al–4V Alloy”; Bansal, Eryilmaz, Blau, evaluated titanium for weight reduction in heavy truck diesel engines.

A wide variety of surface treatments were evaluated for friction and wear including diffusion treatments, hard coatings (TiN and CrN [PVD]), a soft coating (Cu–Ni–In), titanium-matrix TiB2 in situ-formed composite, and shot peening. Two conclusions from the study were reported as:

  • “(b) CrN coated Ti64 specimens had the least amount of wear, followed closely by DLC (diamond-like-carbon) coated Ti64 specimens.
  • (c) Nitrided…specimens yielded the lowest COF, and their wear is also comparable to those of CrN and DLC coated specimens.”

Titanium solution nitriding provided the lowest coefficient of friction (COF) and high wear resistance. The process was performed by Solar Atmospheres in a vacuum furnace using partial pressure nitrogen at temperatures in the annealing range. Solution nitriding is a diffusion process where nascent nitrogen is adsorbed and diffused into the titanium matrix. Like other diffusion processes, the depth of the diffusion zone is dependent on the time of the treatment.

Using Ti-6Al-4V with a core hardness of 30 HRC as the base metal, Solar Atmospheres achieved hardness readings in the mid-60 to upper-60 HRC at a depth of 0.0076mm (0.0003”) followed by a gradual decrease in hardness to the core over a distance of 0.25mm (0.01”). Shorter cycle times produced hardness in the mid-50 to high-50 HRC and shallower total case depths.

Titanium has many beneficial applications from the medical, aerospace, and automotive industries, states the report. Unfortunately, titanium also has poor tribological properties, that is, it has a high COF when in moving contact with structural metals. The result is poor sliding and adhesive wear resistance often resulting in failure by galling (cold welding). In order to provide adequate serviceability for metal-to-metal applications where friction and wear are a concern, some type of surface treatment is typically required.

Solution nitriding is not a coating like CrN or DLC. It is a thermochemical treatment where nitrogen becomes an integral part of the titanium matrix. Unlike a coating, it does not have to initially bond well to work and it will not spall away from the base metal. This is because it is the base metal at the surface; a metallurgical case that significantly strengthens the base metal just as conventional carburizing and nitriding of steel does, allowing for increased service loads along with friction and wear performance properties.

www.solaratm.com  

Contact Don Jordan, Vice President and corporate metallurgist for Solar Atmospheres at [email protected]  .


Subscribe to our FREE e-newsletter

Register to receive our FREE e-newsletter and a complimentary digital subscription to Powder Metallurgy Review magazine:

Your email address:


Useful links: Download PM Review magazine | News headlines | Browse articles 


In the latest issue of PM Review…

Download PDF

Extensive Powder Metallurgy industry news coverage, and the following exclusive deep-dive articles and reports:

  • Powder Metallurgy’s challenge: How does automotive’s reliance on model-based decision making impact our industry?
  • How to make metal powders. Part 4: Centrifugal and other special atomisation methods
  • Precision and energy efficiency in PM press technology: Insights from Ceramitec 2022
  • Historic traditions and new innovations: refractory metals and hard materials at the 20th Plansee Seminar
  • Tailoring a speciality alloy for Additive Manufacturing: From powder production to parameter optimisation
  • Understanding the compaction and sintering effects of four commonly used lubricants in Powder Metallurgy

The latest news from the world of metal powders, delivered to your inbox

Don't miss any new issue of PM Review, and get the latest industry news. Sign up to our weekly newsletter.

Sign up

From the industry…

Discover our magazine archive…

The free-to-access PM Review magazine archive offers unparalleled insight into the world of Powder Metallurgy from a commercial and technological perspective through:

  • Reports on visits to leading PM part manufacturers, metal powder manufacturers and industry suppliers
  • Articles on technology and application trends
  • Information on materials developments
  • Reviews of key technical presentations from the international conference circuit
  • International industry news

All past issues are available to download as free PDFs or view in your browser.

 

Browse the archive

 

Looking for PM production equipment, metal powders, R&D support and more?

Discover suppliers of these and more in our
advertisers’ index and buyer’s guide, available in the back of PM Review magazine.

  • Powders & materials
  • Powder process, classification & analysis
  • PM products
  • Atomisers & powder production technology
  • Compaction presses, tooling & ancillaries
  • Sintering equipment & ancillaries
  • Post-processing
  • Consulting & toll sintering
Download PDF
Share via
Copy link