Mikhail G. Golkovski

Improvement of the hardness and wear resistance of (TiC, TiN)/Ti-6Al-4V surface-alloyed materials fabricated by high-energy electron-beam irradiation

This study is concerned with the microstructural analysis and improvement of the hardness and wear resistance of Ti-6Al-4V surface-alloyed materials fabricated by a high-energy electron beam. The mixtures of TiC, TiN, or TiC + TiN powders and CaF2 flux were deposited on a Ti-6Al-4V substrate, and then the electron beam was irradiated on these mixtures. In the specimens processed with a flux addition, the surface-alloyed layers of 1 mm in thickness were homogeneously formed without defects and contained a large amount (over 30 vol pct) of precipitates such as TiC, TiN, (TixAl1−x)N, and Ti(CxN1−x) in the martensitic or N-rich acicular α-Ti matrix. This microstructural modification, including the formation of hard precipitates and hardened matrices in the surface-alloyed layers, improved the hardness and wear resistance. Particularly in the surface-alloyed material fabricated by the deposition of TiN powders, the wear resistance was greatly enhanced to a level 10 times higher than that of the Ti alloy substrate. These findings suggested that surface alloying using high-energy electron-beam irradiation was economical and useful for the development of titanium-based surface-alloyed materials with improved hardness and wear resistance.

Improvement of hardness and wear resistance in SiC/Ti–6Al–4V surface composites fabricated by high-energy electron beam irradiation

Abstract This study is concerned with the microstructural analysis and the improvement of hardness and wear resistance of SiC/Ti–6Al–4V surface composites fabricated by high-energy electron beam. The mixtures of SiC, SiC+TiC, or SiC+Ti powders and CaF 2 flux were deposited on a Ti–6Al–4V substrate, and then electron beam was irradiated on these mixtures. In the specimens processed with flux addition, the surface composite layers of 1.7–2.1 mm in thickness were homogeneously formed without defects, and contained a large amount (over 44 vol.%) of precipitates such as Ti 5 Si 3 and TiC in the martensitic matrix. This microstructural modification including the formation of hard precipitates and hardened matrix in the surface composite layers could be explained from a Ti–Si–C ternary phase diagram, and greatly improved hardness and wear resistance 2 and 5–25 times higher than the Ti alloy substrate, respectively. These findings suggested that high-energy electron beam irradiation was useful for the development of Ti-base surface composites with improved hardness and wear properties.

Effects of accelerated electron beam irradiation on surface hardening and fatigue properties in an AISI 4140 steel used for automotive crankshaft

This study is concerned with the effects of high-energy accelerated electron beam irradiation on surface hardening and improvement of fatigue properties in an AISI 4140 steel currently used for automotive crankshaft. The 4140 steel specimens were irradiated in air by using a high-energy electron beam accelerator, and then microstructure, hardness, and fatigue properties were examined. Beam power was varied in the range of 5.2∼7.7 kW by changing beam current. Upon irradiation, the unirradiated microstructure containing band structure was changed to martensite and bainite in the carbon-rich zone or ferrite, bainite, and martensite in the carbon-depleted zone. This microstructural modification improved greatly surface hardness and fatigue properties due to transformation of martensite whose amount and type were determined by heat input during irradiation. Thus, high-energy electron beam irradiation can be effectively applied to the surface hardening process of automotive parts. In order to investigate the thermal cycle during electron beam irradiation of quickly rotating specimens, the thermal analysis was also carried out using an analytical computer simulation. Analytical solutions gave information about the peak temperature, heating and cooling rate, and hardened depth to correlate with the overall microstructural modification.

The Structure and Corrosion Resistance of the Coatings Obtained by Non-Vacuum Electron Beam Cladding of the Ti-Nb Powder Mixture on a Titanium Substrates

In this study Ti-Nb coatings formed on the surfaces of cp-titanium plates by electron beam cladding were investigated. It was found that the coatings were characterized by a dendrite structure and a quenched structure was observed in the interdendritic space. The energy dispersive X-ray analysis revealed some differences between the elemental composition of different areas corresponding to dendritic crystals and the space between them. The corrosion resistance of the Ti-Nb alloy obtained on the titanium surface in the concentrated nitric acid was almost 8 times higher than the cp-titanium corrosion resistance.

Welding of a corrosion-resistant composite material based on VT14 titanium alloy obtained using an electron beam emitted into the atmosphere

The study investigates the possibility of inert gas arc welding of a double layer composite material on a titanium base with an anti-corrosive layer obtained by fused deposition of a powder mix containing tantalum and niobium over a titanium base using an electron beam emitted into the atmosphere. Butt welding and fillet welding options were tested with two types of edge preparation. Welds were subjected to a metallographic examination including a structural study and an analysis of the chemical and phase composition of the welds. A conclusion was made regarding the possibility of using welding for manufacturing of items from the investigated composite material.