Abstract
An investigation was conducted to determine the role of Co particles in the WC-Co coating produced with the High Velocity Oxygen-Fuel (HVOF) spraying on microstructure, mechanical and wear properties in a system of type: WC-Co coating/ductlile cast iron. The microstructure of the thermal sprayed WC-Co+Co coating was characterized by scanning electron (SEM) and transmission electron (TEM) microscopes as well as the analysis of chemical and phase composition in microareas (EDS, XRD). For analysis of the quality and adhesion of coatings, the scratch–test was applied. It was found that as a result of the HVOF spray of WC-Co powders with the addition of Co particles, the coatings of low porosity, high hardness, a very good adhesion to the substrate, compact structure with partially molten Co particles and finely fragmented WC particles embedded in a cobalt matrix, coming to the size of nanocrystalline sizes were obtained. Moreover, the results were discussed in reference to examination of bending strength considering cracking and delamination in the system of (WC-Co+Co)/ductile cast iron as well as hardness and wear resistance of the coating. It was found that the addition of Co particles was significantly increase resistance to cracking and wear behaviour in the studied system.
Highlights
A coating material constituting the subject of multiple research works is hard tungsten carbide in the cobalt matrix characterised by high resistance to wear [1]
The aim of the work was to assess the effect of modifying the chemical composition by doping of standard WC-12Co powders with metallic Co particles during consolidation of coatings on ductile cast iron in the process of High Velocity Oxygen Fuel (HVOF) on the structure, mechanical and wear properties of a composite coating system (WC-Co+Co)/ductile cast iron in combination with the analysis of cracking and delamination of the coating in the area of the interface
The following conclusions were made on the basis of the tests and analysis of the results carried out: The composite coating (WC-Co+Co) applied by means of the HVOF method on ductile cast iron is characterised by low porosity, compact structure, good adhesion to the substrate and high hardness
Summary
A coating material constituting the subject of multiple research works is hard tungsten carbide in the cobalt matrix characterised by high resistance to wear [1]. The use of supersonic spray (HVOF) reduced these adverse effects due to the higher velocities and lower temperatures experienced by the powder particles. This results in higher quality, more wear-resistant coatings, with higher levels of retained WC and less porosity [3÷5]. The aim of the work was to assess the effect of modifying the chemical composition by doping of standard WC-12Co powders with metallic Co particles during consolidation of coatings on ductile cast iron in the process of High Velocity Oxygen Fuel (HVOF) on the structure, mechanical and wear properties of a composite coating system (WC-Co+Co)/ductile cast iron in combination with the analysis of cracking and delamination of the coating in the area of the interface
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