Formation mechanism of titanium and niobium carbides in hardfacing alloy

Abstract

The most effective carbide-forming elements titanium and niobium were added into hardfacing alloy. Formation and composition of carbides in the hardfacing alloy were investigated by means of optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and energy-dispersive spectrometer (EDS). Hardness and impact toughness of the hardfacing alloy were measured. The thermodynamics and formation mechanism of carbides were also discussed. It is found that the carbides consist of TiC and NbC which are able to form directly from welding pool during the welding process. The formation mechanism of carbides involves nucleation of TiC followed by epitaxial precipitation of NbC on the surface of TiC. The formation of titanium and niobium carbides can obviously refine the microstructure and deplete the carbon in the matrix. The microstructure transforms to well-distributed carbides and a tough martensite matrix, contributing to a good combination of high hardness and high toughness in the hardfacing alloy.

Forming the structure and the properties of electric arc coatings based on high manganese steel alloyed with titanium and niobium carbides

“…To increase the impact toughness of electric arc coatings by grain refinement the microstructures, the authors [3] propose to introduce Ti and Nb additives allowing for the formation of appropriate carbide phases to the composition of coatings based on low-carbon high-chromium steel. Research results revealed that the addition of a total of ~0.16 % by mass of Nb and ~0.26 % by mass of Ti can increase impact viscosity toughness by 1.6 times, while the hardness of coatings does not change.…”

“…However, under work-ing conditions, in which there are even minor dynamic and (or) cyclic loads, the use of such materials is limited due to the high fragility of coarse-grained metal carbide eutectic structure. For such conditions, it is rational to use electrode materials, the structure of which corresponds to the systems of alloying impact resistant steels [1][2][3][4][5]. The most common representatives of such steels are high-manganese (>13 % by mass of Mn) austenitic steels, which are strengthened during…”

Microstructure and wear resistance of Fe-based hardfacing layer prepared by flux-cored wire feeding MAG welding process

“…Instead, the eutectic structure could be obviously refined and partial chromium carbides were replaced by Ti carbides, which benefited a higher wear resistance. Yang et al [21] prepared the Fe-Cr13-C hardfacing alloy containing Ti and Ni elements. They found that the TiC and NbC were the main carbides that caused the refinement of martensite matrix and therefore contributed to an improved hardness and toughness in the metal.…”

Adição de TiO2, CaCO3 e CaF2 Como Componentes do Fluxo de Arames Tubulares para a Formação de TiC

“…Devido as propriedades mecânicas como elevada dureza e baixa densidade, o acréscimo de titânio com elemento adicional ou principal do fluxo, tem sido amplamente abordado pela literatura [1][2][3][4][5]. Comparado a outros tipos de carbonetos como carbonetos de cromo (Cr7C3), carbonetos de tungstênio (WC) e carbonetos de boro (B4C), os carbonetos de titânio se apresentam com melhores propriedades de resistência ao desgaste [6][7][8].…”