Eventos Anais de eventos
COBEM 2017
24th ABCM International Congress of Mechanical Engineering
Effect of the oxide film on the sliding wear behavior of a CoCrMoSi alloy hardfacing coating
Submission Author:
Ana Sofia D'Oliveira , PR
Co-Authors:
Jonathan Molina Claros, Eduardo Nascimento, Ana Sofia D'Oliveira
Presenter: Eduardo Nascimento
doi://10.26678/ABCM.COBEM2017.COB17-2328
Abstract
Co-based alloys can be used to protect mechanical parts whenever wear, temperature and aggressive environment demands are present individually or together. In the CoCrMoSi alloys the order hard M2Si Laves phase is the main constituent of their microstructure accounting for the superior properties and performance the alloy can offer. This set of features makes CoCrMoSi alloy very attractive for applications that require good wear performance. In spite of that there are very few studies on the wear performance of this alloys, particularly regarding the effect of the oxide film on the wear behavior. An experimental study was carried out to assess the impact of an oxide film former under temperature on the sliding wear of CoCrMoSi – T400 hardfacing coatings. Coatings were processed by Plasma Transferred arc on AISI 304 plates and exposed to 450 and 700 oC for 6 h. Sliding wear tests at room temperature, according to ASTM G99-05 standard, used an alumina pin against the CoCrMoSi alloy coatings in the as-deposited condition and after oxidation. High temperature wear tests were carried out at 700 oC for correlation with oxidized coatings. Wear tests used an applied force of 5 N, tangential velocity of 0,1 ms-1 for a total sliding distance of 1000 m. Coatings were characterized by Scanning Electron microscopy (SEM) using EDS and x-ray diffraction. Oxides present at the surface of coatings after oxidation were identified by Raman spectroscopy. Worn surfaces were analyzed by laser confocal microscopy and scanning electron microscopy. Coatings characterization revealed a Laves phase dendritic structure with an interdendritic eutectic composed of Co solid solution and Laves phase. At 450 oC the main oxides at the surface of coatings were Co3O4, Fe3O, whereas, after oxidation at 700 oC the only oxide present was Cr2O3. Results showed the wear resistance assessed by the friction coefficient and wear rate depends on the characteristics of the oxides formed at the surface. Coatings oxidized at 450C and 700ºC exhibited a small reduction on the wear rate compared to that obtained on as-deposited coatings. A more significant reduction on the wear rate and friction coefficient was obtained after testing at 700ºC. Surface analysis of the worn track revealed that a continuous oxide film forms during high temperature wear tests accounting for the superior performance observed.
Keywords
sliding wear, CoCrMoSi alloys, Coatings
