The comparison and selection of methods for restoration of working surfaces of camshafts of internal combustion engines according to indicators of hardness and wear resistance
Students Name: Moshkovskyi Maksym Oleksandrovych
Qualification Level: magister
Speciality: Motor Vehicle Transport
Institute: Institute of Mechanical Engineering and Transport
Mode of Study: full
Academic Year: 2022-2023 н.р.
Language of Defence: ukrainian
Abstract: The camshaft is a metal rod on which there are cams and bearing necks and eccentricities. At the front end of the shaft there is a pulley or sprocket for driving the camshaft or additional engine mechanisms. The number of cams on the shaft corresponds to the number of valves operating in the engine. Their shape, diameter and construction are also important. During the rotation of the camshaft, the cams push the valve inside the cylinder, that is, the valve opens. The camshaft continues to rotate and the cam continues to move along the valve stem and is returned to its original position by a spring. One cam corresponds to one valve. The time of opening and closing of individual valves is uniform due to the location of the cams on the camshaft. Cams are the most important elements of the camshaft. They are responsible for opening and closing the valves and at the right time. They also affect the filling and emptying of the combustion chamber with gases. The camshaft interacts with the crankshaft. It is the crankshaft that drives the camshaft. During one engine cycle, there are two revolutions of the crankshaft and one revolution of the camshaft. During two complete revolutions of the crankshaft, the camshaft opens the intake valves, closes them, opens the exhaust valves and closes them. After that, the whole process starts again. Object of research: camshafts of internal combustion engines. Subject of research: methods of restoring the working surfaces of engine camshafts. The purpose of the study: to conduct an analysis of the methods of restoration of the working surfaces of the camshafts of internal combustion engines according to the indicators of hardness and wear resistance. The camshaft works in difficult conditions. It is exposed to the forces of friction, bending and twisting. Therefore, the most durable and rigid materials are used in its manufacture. Most often, camshafts are made by forging or casting methods. For their manufacture, low-alloy and carbon steel is used, which can be processed by forging. The working surfaces of the cams, trunnions and eccentricities of such shafts are subjected to the process of flooding and strengthening. If ductile or alloyed cast iron is used for the production of camshafts, then the shafts are cast and then hardened. The working surfaces of the cams and support necks are hardened to a depth of 2...7 mm. The most common methods of restoring cams of camshafts: regrinding to remove traces of wear, metallization, gas surfacing, electric arc, induction, gas flame, plasma and laser surfacing, electric contact sintering of powder materials. Basic words: camshaft, recovery methods, electric arc spraying, gas thermal spraying, air-fuel spraying. List of used literary sources: 1. Войтович А. Мікроструктура наплавлених шарів на основі порошкового дроту Cr10B3 із додаванням Al, Mg / А. Войтович, Р. Михальський, І. Хомич, М. Головчук // Зб. праць XXII відкр. наук.-техн. конф. молодих наук. і спец. ФМІ НАНУ, Львів, 2015. – Л.: ФМІ НАН України, 2015. – С.142–145. 2. Войтович А. А. Підвищення зносостійкості наплавлених шарів методом вертикальної вібраційної обробки / А. А. Войтович, Г. В. Похмурська, Р. Михальський // Тези доп. 12-го Міжнародного симпозіуму українських інженерів-механіків у Львові, Львів, 2015. – Львів: КІНПАТРІ ЛТД. – 2015 – С. 101. 3. Войтович А. А. Методика дослідження абразивного зношування наплавлених шарів / А. А. Войтович, В. М. Гвоздецький, Р. Влах // Тези доп. конф. «Теорія та практика раціонального проектування, виготовлення і експлуатації машинобудівних конструкцій», Львів, 2014. – Львів: НУ Львівська політехніка», 2014. С. 58 – 59. 4. Student, M., Vojtovych, A., Pokhmurska, H. et al. (2019) Mechanical characteristics and wear resistance of the cladding layers obtained by melting of cored wires with simultaneous vibration of substrate. Strojnicky Casopis, 69, 1, 109–122. Voitovych, A.A., Pokhmurs’ka, H.V., Student, M.M., Student, O.Z. (2016) Microstructure and abrasive-wear resistance of the vibration-deposited metal of core wires of the basic Fe–Cr–B system. Ibid, 52, 3, 365–370.