Abstract
The chromium carbide coatings are widely used in the mechanical industry due to its corrosion resistance and mechanical properties. In this work, we evaluated a new source of chromium and silicon with micro-additions of boron on the deposition of multi-component coatings of chromium carbides in W108 steel. The coatings were obtained by the pack cementation method, using a simultaneous deposition at 1000 oC for 4h. The coatings were analyzed by X-ray diffraction, X-ray energy dispersive spectroscopy, optical microscopy, microhardness test method and pin-on-disc wear test. It was found that the coatings formed on W108 steel were mainly constituted by (Cr,Fe)23C6, (Cr,Fe)7C3, Cr5-xSi3-xCx+z, Cr3B0,44C1,4 and (or) Cr7BC4. The carbide layers showed thicknesses between 14 and 15 µm and maximum values of microhardness between 15.8 and 18.8 GPa. Also, the micro-additions of boron to the mixtures showed statistically significant influence on the thickness, microhardness and abrasive wear resistance of the carbide coatings.
Highlights
Cold-work tools are exposed to hard and complex work conditions 1-2
The chromium carbides coatings are obtained by physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma spray, Moltensalt or pack cementation method . 21-28 The chromium-carrier sources used in the pack cementation method are mainly ferrochrome and metallic chromium . 12,29 In a previous study, we reported the reduction products of a concentrate of chromium ore concentrate for this purpose 30
The peaks corresponding to complex oxides of chromium and iron or silicon show relative low intensity, or they are not observed (Figure 1 A and B)
Summary
Cold-work tools are exposed to hard and complex work conditions (high loads, abrasive and adhesive wear, mechanical fatigue, etc.) 1-2. This affects its durability, making necessary its replacement in shorter operating periods. The ceramic coatings have been used for increasing the lifetime of forming tools, cutting tools and machine components 4-5. These layers are mainly constituted by borides, carbides, nitrides and carbonitrides of transition metals 4-7. Its use is limited due to its lower microhardness and abrasive wear resistance in comparison with the carbide layers, nitrides and carbonitrides of other transition elements. The micro-alloying of chromium carbide coatings with one or more elements (titanium, vanadium, boron, silicon, nitrogen, etc.) is one promising alternative to solve this problem . 6,12-19
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