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| Abstract No.: |
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Scheduled at:
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Wednesday, May 05, 2010, Moor Room 2:00 PM
Properties 3
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| Title: |
On the use of nanoindentation and surface scratch testing for HVOF and APS coatings
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| Authors: |
Benedetta Bonferroni / Department of Materials and Environmental Engineering, University of Modena and Reggio Emilia, Italy
Jiri Nohava*/ CSM Instruments SA, Switzerland
Giovanni Bolelli/ Department of Materials and Environmental Engineering, University of Modena and Reggio Emilia, Italy
Luca Lusvarghi/ Department of Materials and Environmental Engineering, University of Modena and Reggio Emilia, Italy
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| Abstract: |
This paper is part of an ongoing research focused on micromechanical characterization of thermal spray coatings by means of instrumented indentation and advanced scratch testing. In previous part of the experiments, cyclic indentation with loads in the range of 0.2 N up to 10 N was done and scratch tests on polished cross sections were performed. In the present study, further results based on nanoindentation and scratch tests on polished surface are presented. The tested coatings were APS and HVOF sprayed ceramics and HVOF metallic alloys. Nanoindentation allowed investigation of individual constituent properties of the coating by probing a very limited number of lamellae which reflect behavior potentially similar to bulk material. Together with the data obtained during indentation experiments in the micro range, this technique provided information about materials response over a broad range of loads, investigating thus the scale effect of the mechanical properties of thermal spray coatings. Scratch tests on the top surface were carried out both in progressive and constant load mode. The first mode provided critical loads at which local surface spallation started to occur, i.e. the resistance to surface cracking and cohesion. The constant load mode, performed at loads lower than the critical ones found in the progressive mode, enabled measurement of the ratio between the cross-sectional scratch area of the side pile-up and the area of the groove and thus calculation of the degree of elasticity and plasticity of the tested coatings. The most significant information from this coupled modes approach was collected on the metallic coatings, which were capable also of relevant plastic deformation.
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