Iranian Journal of Materials Science and Engineering

Recently, wear resistant properties of metallic glasses has attracted a lot of interest. Because the surface of metallic glasses are prone to phase transformation, finding the effects of test condition on structure and wear behavior of metallic glasses is important. In this research, by using an automated electrospark deposition (ESD), a layer of Fe₅₁Cr₁₈Mo₇B₁₆C₄Nb₄ was deposited on AISI 316l stainless steel. Metallographic, scanning electron microscope (SEM) and Energy-dispersive X-ray spectroscopy (EDS) analyses of the coating were conducted for measuring the thickness and analyzing composition of the coating. X-ray diffraction (XRD), Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) investigations showed that the structure of the coating was amorphous. Ball on disc wear tests were conducted in dry and wet conditions and Ringer’s solution was chosen as the wetting agent. The wear test results showed that the coefficient of friction in dry condition was lower than the wet condition and wear modes were fatigue and corrosive wear in dry and wet conditions respectively. SEM and EDS analyses showed different features and elemental inhomogeneity on the surface of the dry wear track, which were not detectable in wet wear track. In addition, activation of diffusion process and formation of carbides and borides were observed on the wear track in dry condition.

The microstructural characteristics, mechanical properties, and wear characterization of air plasma sprayed coatings obtained from Carbon nanotubes (CNTs) reinforced Al₂O₃-3wt%TiO₂ powders were examined at different loading conditions and different percentage proportion of CNTs. The CNTs in the proportion of 2, 4, and 6wt% were used as nanofillers to modify the properties of coatings. The uniform dispersion of CNTs throughout the powder particles can be observed from the SEM micrographs. The porosity of the microstructure of the coatings was measured by image analysis. Also, the mechanical properties such as microhardness and surface roughness were measured by microhardness tester and profilometer, respectively. The wear tribometer was used to analyze the tribology of the coatings by varying different parameters. The different loading conditions used were low load (0.5 kgf), moderate load (1.0 kgf), and elevated load (1.5kgf), respectively. The microhardness showed a slight increase with an increase in the percentage of CNTs proportion. Similarly, the surface roughness value showed a decreasing trend, since the CNTs were filled in the pores. From wear tests, it was observed that the coefficient of friction and wear rate were very less at 6wt% CNTs and 1.5kgf load. This was mainly due to the bridging of CNTs in between the splats. This implies that CNTs were one of the most suitable additives for improving the microstructural and tribological characterization of the ceramic coatings.