In the present study, a mixture of powders (87.9 at.% Ni, 12 at.% Al, 0.1 at.% B) was used as the initial material to produce sintered Ni3Al + B alloy. Spark Plasma Sintering (SPS) method was used to compact the powder. The powder mixtures were previously prepared in two ways: mixing the initial powders in a mortar (М1) and mechanical activation (М2). The microstructure was observed using optical microscope (OM). The addition of small amount of boron to the initial mixture of nickel and aluminum improves the density of the sintered Ni3Al intermetallic compound (98.8%). The results of density, bending and microhardness tests showed, that the provisional three-minute mechanical activation improves almost all properties of the sintered material. The compact obtained by SPS by M2 contributes to the formation of a homogeneous fine-grained structure of the material. It leads to further increase in flexural bending strength up to 2200 MPa. This value is almost 8 times the strength of the intermetallic Ni3Al stoichiometric composition obtained by SPS.
Structural investigations of the materials obtained by surface alloying with titanium-containing powder compositions using industrial electron acceleration were carried out. It was revealed that hardened particles of titanium carbides and borides were formed as a result of high-energy treatment. The highest value of materials studied microhardness was about 8.4 GPa. Friction testing against fixed abrasive particles showed that electron-beam cladding of the titanium and graphite mixture conduced to increasing material wear resistance by a factor of three.
Structural and phase states of wear-resistant coatings obtained by cladding of self-fluxing nickel-based powder mixtures (77 % Ni, 15 % Cr, 2 % B, 3 % Si, 3 % Fe and others) using an electron beam injected in the atmosphere were investigated. The fabricated coatings possessed the complex gradient structure combining hard and ductile components. In the structure of coatings iron borides (Fe2B) surrounded by the ductile matrix represented by Fe, Ni-based γ-solid solution were observed. An increase in the volume fraction of a high strength component in the coating can be reached by additional alloying of the surface by amorphous boron. In this case, microhardness of the coating increases up to 1200 HV.
An investigation of coatings obtained by cladding of boron carbide on a low-alloyed steel substrate by an electron beam injected into the air atmosphere was carried out. It was shown that hardened layers had a heterogeneous structure formed during rapid cooling. It was established that a volume fraction of iron borides in the surface layer had a considerable impact on mechanical properties of the material studied.
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