Thermal spray nanostructured ceramic coatings have proven to possess characteristics that are favorable for wear resistance applications.  A unique characteristic of improved toughness without compromising on hardness has led to dramatic improvements in abrasion-resistance, as well as low- and high-impingement angle slurry erosion [1-3].  An added advantage of these novel ceramic coatings relates to the reduced surface finishing time required to attain target smoothness (reductions of 40 % have been observed). The time and effort saved in surface finishing translates to notable cost savings.  There are currently thousands of military and industrial components that are benefiting from nanostructured coatings. 

Examples of military applications include wear and corrosion resistant nanostructured ceramic coatings for ship bearing journals, submarine ball valves, and ship reduction gear in air conditioner unit [4].  The United States Navy is saving tens of millions of dollars annually from the use of these coatings.

Thousands of ball valves and numerous stirring blades in high pressure acid leach and pressure oxidation facilities around the world are coated with nanostructured ceramic coating [5].  These components are exposed to sliding, abrasion, and slurry erosion conditions, all within a very corrosive environment.

Initial research on the development of a thermal spray nanostructured WC-base cermet coating was not successful due to the high level of carbide degradation.  However, recent work carried out by FW Gartner and Perpetual Technologies on depositing nanostructured WC-Co have led to a higher retention of WC nanoparticles within the coating.  Samples of these coatings were tested at Syncrude Canada’s research laboratory.  The very promising result is shown in the figure below where the red column represents the weight loss of the latest FWG-PT nanostructured WC-12Co coating against three-body abrasion compared to those of other thermal sprayed WC-12Co coatings in Syncrude Canada’s database.  In fact, the wear loss is low enough to be approaching those found in welded coatings such as plasma transferred arc (PTA) process.

FW Gartner and Perpetual Technologies are continuing their effort towards further enhancing the performance of nanostructured carbide-base cermet coatings.  Several examples of target applications include offshore gate valves, bitumen pump impellers, power valves, and slat and flap tracks.

When the right combination of material(s) selection, spray process/parameters, and powder characteristics are attained, nanostructured coatings can be developed for existing and/or future applications that require superior wear resistance. 

REFERENCES

1      Lawrence T. Kabacoff, “Nanoceramic Coatings Exhibit Much Higher Toughness and Wear Resistance than Conventional Coatings”, The AMPTIAC Newsletter, Spring 2002, Volume 6, Number 1.

2      M. Gell with E.H. Jordan et al., “Fabrication and Evaluation of Plasma Sprayed Nanostructured Alumina-Titania Coatings with Superior Properties,” Mater. Sci. Eng., A301, pp. 80-89, 2001.

3      G.E. Kim, “Thermal Sprayed Nanostructured Coatings: Applications and Developments”, Chapter 3 of Nanostructured materials: processing, properties, and applications, edited by C.C. Koch, 2007.

4      J. Pappalardo, “U.S. Navy Finding New Applications For Advances In Nanotechnology”, National Defense Magazine, October 2004.

5      J. Williams, G.E. Kim, and J. Walker, “Ball Valves with Nanostructured Titanium Oxide Coatings for High-Pressure Acid-Leach Service: Development to Application”, Proceedings of Pressure Hydrometallury 2004, Banff, Alberta, Canada, October 23-27, 2004.

George E. Kim, Ph.D.

F.W. Gartner

Perpetual Technologies, Inc.

email: gkim@perpetualtech.ca