Formation of Structure and Properties of Boron-Rich Fe–B–C Alloys Alloyed with Cr, V, Nb or/and Mo

Abstract

The effects of substitution of Fe in the boron-rich Fe-B-C alloys, containing 10.0-14.0% B and 0.1-1.2% C, 0-5.0 % Cr, V, Mo or/and Nb (in % wt.), are studied with combined analysis of optical microscopy, X-ray diffractometry, scanning electron microscopy, energy dispersive spectroscopy. The microstructure of the master Fe-B-C alloys consists mainly of primary dendrites of Fe(B, C) solid solution and Fe 2 (B, C) crystals peritectically formed from Fe(B, C) phase and the rest of the melt. As found, chromium or vanadium have high solubility in the constituent phases of the Fe-B-C alloys, with preferential solubility observed in the Fe(B, C) dendrites, where Cr or V occupy Fe positions. The addition of Cr or V to the Fe-B-C alloys helps to modify their brittleness: while it slightly decreases microhardness values, addition of these elements notably improves the fracture toughness of the constituent phases. Molybdenum or niobium are shown to be present in secondary phases identified as Мо 2 В, Мо 2 (B, C) or NbB 2 , respectively. The level of Mo or Nb contents in the Fe(B, C) and Fe 2 (B, C) solid solutions and quantity of the observed secondary phases indicate a very small Mo and no Nb solubility in the constituent phases. The Mo or Nb enhances a hardness of the master Fe-B-C alloy due to secondary phases' precipitation. To enhance performance characteristics of the boron-rich Fe-B-C alloys, the 1.0-2.0% Cr, 0.5-1.0%V, 1.0-3.0% Nb, 1.0-3.0% Mo are simultaneously added to the master alloy. The properties improve due to the formation of Cr-and Vcontaining Fe 2 (B, C) and Fe(B, C) solid solutions as well as Mo-and Nb-based secondary phases. The developed multicomponent alloy is recommended as a filler of macroheterogeneous composite coatings for strengthening of parts

Effect of Exothermic Additions in Core Filler on Arc Stability and Microstructure during Self-Shielded, Flux-Cored Arc Welding

“…For the flux-cored arc welding process of filler materials, melting is mainly carried out by arc welding [47,48]. Additionally, an important aspect is the study of the mechanical properties of the deposited metal [49][50][51][52]. The final microstructure and mechanical properties depend on the cooling conditions of the deposited metal [53,54] and heat input.…”

Untitled

“…In this case, this system alloying with elements improving its plastic properties and corrosion resistance is very interesting. Modern researchers mostly focused on alloying boron-containing alloys with a chromium [78], titanium [79][80][81], aluminium [76], vanadium and molybdenum [82][83][84]. However, the formation of chromium-rich borides, such as (Fe, Cr)2B, reduces the content of corrosion-resistant alloying elements in the matrix, and therefore reduces corrosion resistance [85].…”