NANOSTRUCTURED COATINGS FOR AUTOMOTIVE APPLICATIONS
Tuesday, April 13, 2010 at 08:25PM In addition to reducing the weight, life extension of modern automotive systems are key sought after demands. Life extension can often be addressed by protecting against corrosion and/or wear. Nanostructured ceramic coatings have proven to enhance the life and wear resistance of severe-service applications [[i]]. Nanostructured metal coatings have been successfully developed and tested for various applications; the results indicate promising results for refurbishment and corrosion/oxidation protection applications [[ii]]. The information below will provide a snapshot at some possible matches between these novel class of coatings and specific and general automotive demands.
A very interesting application that has several ramifications towards reducing energy cost and material wear in powertrain applications has been studied by several researchers [[iii], [iv]]. They have demonstrated the advantages of APS depositing a metal-matrix composite (MMC) coating onto cylinder liner surfaces of heavy duty diesel truck engines. The advantages include: reductions in wear, blow-by and oil consumption. Based on the results observed in nanostructured MMC (i.e., WC-Co) coatings [[v],[vi]], there may be an opportunity to further enhance the positive attributes of the MMC coating presented by Ernst et al. In addition to further reducing wear, blow-by and oil consumption, there may also be an advantage in attaining a superior finish with reduced depth of cut with the nanostructured MMC coating. Other automotive components that could benefit from a similar nanostructured coating include: cylinder rods, plungers, and shafts; diesel valves; and bearing areas.
In pursuit of weight reduction in automotives, more lightweight materials are being incorporated. Amongst these lightweight materials, aluminum alloys are gradually being introduced. In many instances the aluminum alloys can replace steel in so far as matching its strength. However, there is a compromise with respect to wear resistance of aluminum alloys. To address this issue, a thermal spray hard coating such as CrC-NiCr has been applied and tested against wear and corrosion [[vii]]. According to the authors of this work, the coated prototypes passed both the dynamical and salt fog corrosion tests. Once again, based on the results of nanostructured cermet MMCs, one may expect to improve resistance against wear, impact and localized corrosion by using a nanostructured coating of the same material. Another weight saving automotive application that could benefit from the incorporation of a nanostructured coating is Al-MMC brake discs. By using a nanostructured aluminum oxide coating instead of its conventional counterpart, the same improvements over iron brake discs can be retained, i.e., improved fuel economy, better acceleration, exceptional wear resistance, a high coefficient of friction, improved braking performance. In addition, the wear and impact resistance of the nanostructured aluminum oxide will be further enhanced.
Refurbishing worn components can lead to substantial cost savings. For automotive applications, thermal spray repair of worn shifter forks, crankshafts, bearing regions, and transmission shafts have been successfully implemented. By using nanostructured metal coatings, one may be able to, in some cases, surpass the original performance characteristics of the repaired regions with respect to strength, wear and corrosion.
Turbochargers in engines, exhaust systems, manifolds can all benefit from the incorporation of nanostructured TBC system. Nanostructured yttria partially stabilized zirconia (YPSZ) and nanostructured MCrAlYs may respectively provide lower thermal conductivity and superior oxidation resistance, as compared to the existing TBC system [[viii]]. In addition to improved engine performance, these coatings may reduce cockpit temperatures and extend the life of the components.
Due to the widespread use of automotive systems for all levels of transportation, any improvements in their performance, life, and/or fuel consumption can lead to enormous implications with respect to individual/global economics and environmental impact.
REFERENCES
[i] 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.
[ii] G.E. Kim, NANOSTRUCTURED MCrAlYs, available at: http://blog.fwgartner.com/blog/2009/11/23/nanostructured-mcralys.html, 2009.
[iii] P. Ernst, G. Barbezat, “Thermal spray applications in powertrain contribute to the saving of energy and material resources”, Surface & Coatings Technology 202 (2008) 4428–4431
[iv] B. Gerard, “Application of thermal spraying in the automobile industry”, Surface & Coatings Technology 201 (2006) 2028–2031
[v] G.E. Kim, NANOSTRUCTURED COATINGS AND THEIR BENEFITS FOR WEAR APPLICATIONS, available at: http://blog.fwgartner.com/blog/2010/1/13/nanostructured-coatings-and-their-benefits-for-wear-applicat.html, 2010.
[vi] B. Zhang, X.B. Liu, An Investigation of Microgrinding of Nanostructured Material Coatings, Presented at UEF Conference on Novel Synthesis and Processing of Nanostructured Coatings for Protection Against Degradation, Davos, Switzerland, 2001.
[vii] A. Wank, B. Wielage, T. Grund, C. Rupprecht, K. Angermann, T. Schnick, “Local wear protection for demountable automotive aluminum draw bars by thermal spray coatings”, From: ITSC 2005: Thermal Spray connects: Explore its surfacing potential! (2005)
[viii] G.E. Kim, POTENTIAL FOR NANOSTRUCTURED COATINGS IN GAS TURBINE ENGINES, available at: http://blog.fwgartner.com/blog/2010/2/12/potential-for-nanostructured-coatings-in-gas-turbine-engines.html, 2010.
George E. Kim, Ph.D.
F.W. Gartner
Perpetual Technologies, Inc.
email: gkim@perpetualtech.ca
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