Deposition and properties chromium oxide-based coatings by plasma spray process
Steduto, Daniel (2020)
2020
Materiaalitekniikan DI-tutkinto-ohjelma - Degree Programme in Materials Engineering, MSc (Tech)
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2020-04-29
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202004233603
https://urn.fi/URN:NBN:fi:tuni-202004233603
Tiivistelmä
The purpose of this study was to investigate the influence of powder composition and type on formation, structure and properties of selected chromia based plasma sprayed coatings. Pure Cr2O3 coating was compared to chromia coatings containing Al2O3, TiO2 and ZrO2, all deposited under identical conditions. Feedstock powders were characterized in terms of microstructure, phase structure, chemical composition and particle size distribution. Coatings' characterization started with microstructures and porosity by using optical and scanning electron microscopy, the phase composition was studied by X-ray diffraction analysis. Coating microhardness (HV0.3) was also measured. Tribological investigation included sliding wear (ASTM G99), abrasive wear (ASTM G65), complemented by scratch tests.
Wear occurred due to brittle fracture both in abrasion and sliding condition. Coatings that exhibited good sliding wear behaviour suffered the highest material loss in abrasion tests. Pure chromia coating displayed the lowest sliding wear rate of 4.32×10-8 mm3/(N·m), whereas, when alloyed with other oxides, the sliding wear resistance worsened. The opposite is true under abrasion conditions. Fundamental abrasive wear mechanisms were simulated by scratch testing; indeed, coatings which performed the best in the ASTM G65 abrasion test displayed less damage in the scratch test. Coatings that contained zirconia exhibited the best abrasion resistance, because, as revealed by single-asperity scratch tests, zirconia-rich splats could restrain intergranular brittle fracture.
Wear occurred due to brittle fracture both in abrasion and sliding condition. Coatings that exhibited good sliding wear behaviour suffered the highest material loss in abrasion tests. Pure chromia coating displayed the lowest sliding wear rate of 4.32×10-8 mm3/(N·m), whereas, when alloyed with other oxides, the sliding wear resistance worsened. The opposite is true under abrasion conditions. Fundamental abrasive wear mechanisms were simulated by scratch testing; indeed, coatings which performed the best in the ASTM G65 abrasion test displayed less damage in the scratch test. Coatings that contained zirconia exhibited the best abrasion resistance, because, as revealed by single-asperity scratch tests, zirconia-rich splats could restrain intergranular brittle fracture.