Abstract No.:
3620

 Scheduled at:
Friday, May 23, 2014, Hall H2 12:00 PM
Tribological Coatings


 Title:
Influence of cold, warm and plasma sprayed layers on high-cycle fatigue properties of steel specimens

 Authors:
Jan Cizek* / Institute of Materials Science and Engineering, Brno University of Technology, Czech Republic
Michaela Matejkova / Institute of Materials Science and Engineering, Brno University of Technology, Czech Republic
Charles M Kay/ ASB industries, US
Jeganathan Karthikeyan/ ASB Industries, US
Seiji Kuroda/ National Institute of Materials Science, Japan
Ondrej Kovarik/ Dept of Materials, FNSPE, Czech Technical University, Czech Republic
Jan Siegl/ Dept of Materials, FNSPE, Czech Technical University, Czech Republic
Khiam Aik Khor/ Nanyang Technological University, Singapore
Ivo Dlouhy/ Institute of Materials Science and Engineering, Brno University of Technology, Czech Republic

 Abstract:
In the presented study, the influence of thermally sprayed coatings on fatigue behavior of coated bodies was studied.

Commercial-grade titanium powder was deposited onto low-carbon steel flat specimens using four thermal spray technologies: plasma spray, low-pressure and portable cold spray, and warm spray. The specimens were then subjected to strain controlled cantilever-beam cyclic bending test in a dedicated in-house built device. The crack propagation was monitored by observing the changes in the resonance frequency of the samples. A stop-condition corresponding to approximately 40-60% specimen cross-section damage was used to define the fatigue life of the specimen. Such fatigue life relative to the fatigue life of plain untreated specimens was considered the main performance indicator.

It was found that the grit-blasting procedure did not alter the fatigue properties of steel specimens considerably (5% increase), while deposition of the coatings via all technologies significantly increased the measured fatigue lives. The three high-velocity technologies led to a relative lives of 202% (low-pressure cold spray), 220% (portable cold spray), and 383% (warm spray, the highest recorded increase of the fatigue performance) and the deposition using plasma spray led to an increase of relative lives to 316%.

The fatigue life increase of the sets deposited by the kinetic technologies is probably caused by a combination of the presence of homogeneous fatigue resistant coating and induction of peening stresses into coatings and substrates via the impingement of the high-kinetic energy particles. Given the intrinsic character of the plasma jet (low-velocity impact of semi/molten particles), the influence of phase transformed plasma sprayed coatings on fatigue lives must be explained by a different mechanism.


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