Horpenko A. Influence of Welding Defects on the Fatigue Strength of the VT22 Titanium Alloy with a Restored Surface

Українська версія

Thesis for the degree of Doctor of Philosophy (PhD)

State registration number

0825U001402

Thesis Registration Form

0825U001402.pdf

Applicant for

Artem O. Horpenko

Specialization

132 - Матеріалознавство

Specialized Academic Board

PhD 8660

National Technical University of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute»

Essay

The dissertation of Artem Horpenko is devoted to the experimental and theoretical study of the influence of restorative welding defects on the fatigue strength of titanium alloys, particularly the VT22 alloy, using VT22sv and SP15sv filler wires. The research investigates microstructural changes, phase composition, and mechanical properties in the weld zone and heat-affected zone after welding with an external magnetic field and subsequent local heat treatment. The relationship between welding parameters, structural homogeneity, microhardness characteristics, and fatigue durability of the samples has been established. Fatigue tests were conducted on blade-type specimens with a central hole under cyclic loading. It was found that the main factors reducing fatigue strength were pores in the near-surface layer, microstructural inhomogeneities in the heat-affected zone, and the presence of zones with different etchability and reduced microhardness. A method for detecting zones with different etchability without chemical etching based on changes in reflectivity during grinding was developed. It was shown that optimizing local heat treatment parameters allows minimizing structural defects, stabilizing phase composition, and increasing the fatigue strength of restored samples. The maximum number of cycles to failure reached 24,796 for specimens with SP15sv filler and 28,388 for specimens with VT22sv filler. The obtained results are of significant practical importance for improving the technology of restoring titanium aircraft components operating under cyclic loading conditions and enhancing their service life. Keywords: welding defects, local heat treatment, fatigue strength, titanium alloys, filler wire, microstructure, phase composition.

Thesis supervisor

Oleksandr M. Donii

Official opponents

Serhii L. Shvab
Mykhailo M. Voron

Reviewers

Myroslav V. Karpets
Anatolii V. Minitskyi

Research papers

Горпенко А.О., Семенець О.І., Доній О.М., Валуйська К.О. Вплив стану поверхні деталей шасі з високоміцного титанового сплаву ВТ-22 в процесі випробувань на втому // Успіхи матеріалознавства, 2021, № 2, стр. 45-53.

Горпенко А.О., Семенець О.І. Вплив дефектів зварювання на втомні показники зразків зі сплаву ВТ-22 при застосуванні відновлювального наплавлення присадковими дротами. Успіхи матеріалознавства, 2023, № 7, стр. 27-36.

Горпенко А.О., Семенець О.І. Вплив стану поверхні на втомні показники зразків з отвором зі сплаву ВТ22 при застосуванні відновлювального наплавлення присадним дротом зі сплаву СП15СВ // Автоматичне зварювання, 2024, №6, стр. 35-42.

Horpenko A.O., Semenets O.I. The Effect of Reducing Surface Cladding with VT22sv Filler Wire on the Fatigue Performance of Samples Made of VT22 Alloy // Metallofiz. Noveishie Tekhnol., 2024, vol. 46, №11, pp. 1095–1110.

Gorpenko A., Semenets O., Doniy O. Effect of restorative cladding with VT22sv filler wire and local heat treatment on the fatigue performance of VT22 alloy samples with a hole // VII International Conference “Welding and Related Technologies”, 7–10 October 2024, Yaremche, Ukraine. – P. 16.

Gorpenko A., Semenets O., Doniy O. The impact of welding defects on the fatigue properties of VT-22 alloy samples using repair welding with filler wires // ІІІ Міжнародна науково-практична конференція «Modern challenges and achievements of the scientific community of the 21st century», 16–18 October 2024, Narva, Estonia. – P. 171.

Gorpenko A., Semenets O., Doniy O. Effect of the chassis parts surface condition from high-strength titanium alloy VT-22 in the process of fatigue tests // IV Міжнародна науково-практична конференція «The impact of scientific research on the development of the modern world», 23–25 October 2024, Dubrovnik, Croatia. – P. 237.

Gorpenko A., Semenets O., Doniy O. The influence of surface defects on fatigue performance of VT22 alloy samples with holes using restorative welding with SP15SV filler wire // VI Міжнародна науково-практична конференція «Scientific research in the era of digital technologies: challenges and opportunities», 6–8 November 2024, Barcelona, Spain. – P. 307.

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