Abstract
MoS2 powder has been used to form "self-lubricating" composite coatings, which are very useful to increase the lifetime of machines where liquid lubricants cannot be used. In this work, amorphous overspray powder of Fe60Cr8Nb8B24 (at%) alloy was mixed with 5wt.% MoS2 powder and it was used to produce single tracks on AISI 1020 steel substrates by laser cladding. The tracks were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Vickers microhardness. It was observed α-Fe, an Nb-rich intermetallic and MoS2 particles in the tracks, regardless of laser parameter used. DSC analyses proved the presence of amorphous phase for samples produced with parameters 200W/33.3mm/s, 600W/100mm/s, 800W/100mm/s and 800W/150mm/s. The tracks produced with larger power (800W) and higher scanning speeds (100 and 150mm/s) exhibited a better integrity and homogeneity, lower dilution and presence of amorphous phase, being these parameters considered the most appropriate to produce composite coatings of Fe60Cr8Nb8B24 (at%)/5wt% MoS2 containing amorphous phase. Hardness tests showed that the single tracks produced are harder than the substrate, for example, the track produced with 800W/150mm/s exhibits hardness six times higher than the steel substrate, 1200 HV0.3 and 200 HV0.3, respectively.
Highlights
Fe-based bulk metallic glasses (BMG) are promising materials to be used as coatings because they exhibit very high mechanical strength combined with high corrosion resistance[1]
The Fe60Cr8Nb8B24 alloy used in this work was spray formed following a similar procedure found in literature[7,8,9,10] in an induction melting furnace using as raw materials a ferritic stainless steel (FSS) AISI 430 with 13% Cr content, combined with additions of Fe-67%Nb and Fe-14%B alloys
The single tracks were prepared by placing a 0.2 mm thick layer on the AISI 1020 substrate. These layers were clad using different laser powers (200, 400, 600 and 800 W) and scanning speeds (150, 100, 66.7, 33.3 and 16.6 mm/s), which resulted in a variation of the energy density from 7 to 240 J/mm[2]
Summary
Fe-based bulk metallic glasses (BMG) are promising materials to be used as coatings because they exhibit very high mechanical strength (near theoretical limits) combined with high corrosion resistance[1]. Some obstacles for their wide use in structural applications are their relatively high production cost and low ductility[2]. Laser Cladding of Fe-based Metallic Glass/MoS2Self-lubricating Composites: Effect of Power and Scanning. Speed to investigate their influence in the microstructure, phase formation and mechanical properties
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