INFLUENCE OF THE STRENGTHENED SURFACE LAYER BY ELEMENTS INTERSTITIAL OF (O, C) ON THE FRACTURE RESISTANCE OF TITANIUM DURING FATIGUE AND IMPACT LOADS

Authors

DOI:

https://doi.org/10.30838/J.PMHTM.2413.290920.74.671

Keywords:

titanium alloy, gaseous medium, surface layer, oxygen, carbon, fatigue life, impact strength

Abstract

The purpose of the study to establish the effect of the strengthened near-surface layer by penetration elements (O, C) on the fatigue life of a clean bend at elevated temperatures (up to 350 °C) and impact strength at room temperature of titanium. The Methodology. We studied samples of industrial titanium alloys of - (VT5-1 and PT-7M), pseudo--(OT4-1), ( + )-(VT14 and VT19) classes. After fabrication, the samples were annealed in vacuum according to the mode: T = 800 °C, τ = 5 h, P = 0,05 MPa. Thin-sheet samples (~ 1 mm) were saturated with oxygen and carbon-containing media to form a gradient hardened near-surface layer without a phase film. Results. It was revealed that the fatigue life in the temperature range T = 20...150 °C of VT1-0 titanium is not sensitive to the test temperature during the formation of the «optimal» level of surface hardening (K = 70 %, l = 30 μm) after treatment in oxygen-containing media. At temperatures Т = 150...400 °С, the dependence of the durability of titanium has the same decreasing character for all studied levels (K = 70 % and K = 140 %) of surface hardening. It is revealed that hardening (K = 70 %, l = 30 µm) of the surface layer formed in oxygen- and carbon-containing gas media increases the impact toughness by 4..6 % relative to the untreated (K = 0 %) state. Originality. The parameters of the hardened layer (K = 70 %, l = 30 μm), which contribute to an increase in fatigue life by 15...25 % at pure bending at elevated temperatures T = 150 °C, have been established, and it has also been shown that such a layer does not lead to a decrease in the impact titanium viscosity VT1-0. Practical value. The formation of a strengthened near-surface layer (K = 70 %, l = 30 μm) can be used in non-thin-sheet products made of VT1-0 titanium alloy to increase the durability under a cyclic load up T = 150 °C or resistance to shock loading.

Author Biographies

V. S. Trush, Karpenko Physico-Mechanical Institute of the NAS of Ukraine

Department of Materials Science Fundamentals of Surface Engineering, Cand. Sc. (Tech.), Senior Researcher

V. M. Fedirko, Karpenko Physico-Mechanical Institute of the NAS of Ukraine

Department of Materials Science Fundamentals of Surface Engineering, Dr. Sc. (Tech.), Prof., Chief Researcher

А. G. Lukyanenko, Karpenko Physico-Mechanical Institute of the NAS of Ukraine

Department of Materials Science Fundamentals of Surface Engineering, Cand. Sc. (Tech.), Senior Researcher

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Published

2020-09-22

Issue

No. 3 (2020): Metal Science and Heat Treatment of Metals

Section

Technical science

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