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Thermal spray and WC-Co based coatings are widely used in areas subjected to abrasive wear. Commercial  cermet thermal spray powders for HVOF are relatively expensive. Therefore applying these powders in cost-sensitive areas like mining and agriculture are hindered. Nowadays, the use of cheap iron based self-fluxing alloy powders for thermal spray is limited. The aim of this research was to study properties of composite powders based on self-fluxing alloys and recycled cermets and to examine the properties of thermally sprayed (HVOF) coatings from composite powders based on iron self-fluxing alloy and recycled cermet powders (Cr₃C₂-Ni and WC-Co). To estimate the properties of  recycled cermet powders, the sieving analysis, laser granulometry and morphology were conducted. For deposition of coatings High Velocity Oxy-Fuel spray was used. The structure and composition of powders and coatings were estimated by SEM and XRD methods. Abrasive wear performance of coatings was determined and compared with wear resistance of coatings from commercial powders. The wear resistance of thermal sprayed coatings from self-fluxing alloy and recycled cermet powders at abrasion is comparable with wear resistance of coatings from commercial expensive spray powders and may be an alternative in tribological applications in cost-sensitive areas.

DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1338

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The aim of the current study was to elaborate and compare abrasive wear resistance of thick coatings deposited with different hardfacing technologies. To produce metal matrix composite (MMC) coatings commercial iron and nickel based powders with recycled hardmetal content of 40 vol. % were studied. For deposition technologies plasma transferred arc (PTA) hardfacing, high-velocity oxy-fuel (HVOF) spraying were used. The microstructure of produced thick coatings was examined, including the distribution of hard phase and homogeneity of metal matrix. Micromechanical properties, including hardness and elastic modulus of features were measured by universal hardness measurements. Furthermore, behavior of coatings subjected to abrasive rubber-wheel wear (ARWW) and impact wear (AIW) tests were studied. Wear resistance of experimental PTA hardfacings at low velocity ARWW and AIW tests notably exceeds that of HVOF sprayed coatings. Wear mechanism dominating at abrasive wear in most cases is the removal of metal matrix due to lower hardness. Assignment of hardmetal waste as initial material can significantly decrease the cost of production, improve the mechanical characteristics of coatings and consequently increase their wear resistance. Results indicate, that the choice of matrix for the same reinforcements can also be as an important factor for combating abrasive wear. Fe-based thick coating, produced by PTA is more wear resistant compared to the Ni-based ones.

The aim of this research was to optimize the mechanically activated synthesis (MAS) technology of the Cr3C2-Ni powder intended for thermal spraying. The MAS production route included ball milling for 72 h (ball-to-powder ratio 20:1) and sintering under 1075 °C in vacuum for 4 h. Sintered compact was crushed, classified by sieving to obtain the fraction suitable for thermal spraying (20–45 μm). The morphology and the phase composition of the powder were analyzed by a scanning electron microscope (SEM) and X-ray diffraction (XRD). The optimal Cr:C ratio found was 7:1. The powder had an equiaxial or a slightly elongated lamellar shape, Cr3C2 carbides in a single powder particle had an elongated shape. The principal phases in the optimized powder were Cr3C2, Cr7C3 and Ni (Cr) solid solution. Coatings from the manufactured powder were produced by the high velocity oxy-fuel (HVOF) spraying. The abrasive wear tests were carried out according to standard ASTM G65. The wear tests showed that the sprayed coatings from the experimental powder exhibited about five times higher wear rate at abrasive wear conditions than the coatings from the reference commercial powder.