Influence of Al2O3 Particle Size on Microstructure, Mechanical Properties and Abrasive Wear Behavior of Flame-Sprayed and Remelted NiCrBSi Coatings

Abstract

The influence of micrometric alumina (low surface area-to-volume ratio) and nanometric alumina (high surface area-to-volume ratio) on microstructure, hardness and abrasive wear of a NiCrBSi hardfacing alloy coating applied to an AISI 304 substrate using flame spraying (FS) combined with surface flame melting (SFM) is studied. Remelting after spraying improved the mechanical and tribological properties of the coatings. Microstructural characterization using XRD, SEM and EDS indicated that alumina additions produced similar phases (NiSi, Ni 3 B, CrC and Ni 31 Si 12) regardless of the alumina size, but the phases differed in morphology, size distribution and relative proportions from one coating to another. The addition of 12 wt.% nanometric Al 2 O 3 increased the phases concentration more than five-to sixfold and reduced the hard phases size about four-to threefold compared with NiCrBSi + 12 wt.% micrometric Al 2 O 3. Nanoalumina led to reduced mass loss during abrasive wear compared to micrometric alumina and greater improvement in hardness.

Wear Resistance of Multi-Component Composite Coatings Applied by Concentrating Energy Flows

“…The introduction into the composition of the materials of the self-fluxing additives (B, Si, C, etc.) is one way to maximize the storage of the beneficial properties of the individual components of layering material in the coating [13][14][15][16][17]. The securing the necessary performance characteristics and adhesion of the surface layer in the present work is solved by the using of Co, Ni, Cr forming unlimited solutions in the iron [14][15][16]18,19].…”

Considerations for the Selection of Materials for Electrical Spark and Gas Flame Spraying Deposition on Structural Steels

“…For this reason, technological additives such as B, Si, C, Al 2 O 3 , Cu, C, Al and others can be incorporated into the material composition with different purposes. For example, the introduction of B, Si, C reduces the formation of oxides, and at ESD also reduces the erosion resistance of the laminating electrodes [ 22,[35][36][37][38]39 ]. At the same time, the boron serves as a donor for the formation of wear-resistant borides in the layer, the carbon -as an antidecarburization during the transfer process, and for the additional formation of dispersed carbides in the process of forming the coating.…”

“…Cu contributes to reducing the size of the grains in the layer; Aluminum increases the yield strength limit and, because of its low melting temperature, helps to increase the transfer to the substrate. Due to their good wear and corrosion resistance, Ni-C-rB-Sibased alloys are commonly used in the GFS on steels [35][36][37][38][39][40]. Essential elements in these compositions are B and Si.…”

“…Further, they promote wetting of the substrate by reducing Ni, Co, Fe and Cr oxides, controlling surface tension and fluidity of the melt .The low melting point of NiCrBSi alloys as well as the fluxing effect of the Si and B allows these materials to be deposited by flame spray followed by fusing and welding the powders. An increase in the amount of chromium, boron and carbon increases the amount of solid carbides and borides, respectively [15,[35][36][37][38][39][40].…”

“…Еxperience has proved these alloys are a good choice for components in the presence of hard particles. Higher hardness and abrasion resistance is ensured with additions of hard-alloy compounds [15,22,2,[35][36][37][38][39][40].…”