A metalloceramic NiCrBSiFe−WC coating on structural steel 40Kh was prepared by the method of laser cladding. The cladding was performed using a multichannel continuous СО 2 laser radiation using the complex of ALTKU3 model produced by LLC "Centre of laser technologies", the city of Vladimir. The complex includes a multichannel (40 rays) СО 2 laser with the output power of 3 kW and a technological stand with five coordinates for ray manipulation and with two ones for manipulation of the piece under processing. The prepared samples were examined metallographically. It is shown that at optimal modes a practically pore-free coating is formed with a minimal penetration into the base ensuring metallurgical fusion. According to the X-ray spectral microanalysis data the chemical composition is practically the same as that of the raw powder. In particular, the content of iron in the granules and in the matrix is nearly the same (about 4…5 %). Due to the automatization of the processing by crossed rollers the sample surface after cladding is nearly flat and only requires a slight machining. The thickness of the cladding layer is about 700 μm in one pass. No cracks in the plane of the sample were observed. The weld junction demonstrates the same structure lengthwise thus indicating a high uniformity of the heat input during the cladding. The size of the thermal effect zone in the substrate is about 450 μm. The laser cladding of the highly alloyed powder of the system NiCrBSiFe−WC onto the structural steel by means of the multichannel СО 2 laser makes it possible to obtain a high-quality wear-proof coating since, in contrast to single ray lasers, it provides a high uniformity of integral heat input in the processing zone.

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Studies are carried out on the microstructure and micro-hardness distribution of structural steel 30HN3А samples hardened by laser quenching by means of continuous radiation from a multi-channel 48 rays CO 2 laser system CLT-Yu-5. To provide the formation of a uniform structure, hardness and depth distribution in the hardened material layer a laser emitter was used with four plug-in radiating tubes arranged one into another in an octahedral configuration (patent RF № 2580350). An important role of a high uniformity of the integral heat input across the hardening zone width on the uniformity of properties of the hardened layer is demonstrated. It was found that in the hardened area a finely dispersed martensite structure was formed. The carbides contained in the initial structure of sorbite dissolve not completely during laser hardening. They are characterized by a globular form and size of 0.2…0.3 µm. The microhardness of steel in the hardened area was about 6800 MPa. The thickness variation of the hardened layer, which is characterized by the ratio between minimal, h min , and maximal, h max , depths, is equal to 0.76 at h max = 1050 µm. A reduction in microhardness in a tempering zone formed between two successive hardened bands down to the values of 5500…6000 MPa was found. The width of this tempering zone is about 1.8 mm. The decrease of microhardness in this zone is due to a dissociation of the martensite and formation of tempering troostite structure. Lamellar carbides are formed during this process. Steel in the laser hardened area has a favorable structure in terms of the strength and durability. Thus, hardening of steel by means of multi-channel CO 2 laser systems provides wide opportunities in improving of material properties and is recommended for hardening of expensive machine parts increasing their service lifetime.Keywords: multi-channel СО 2 laser, laser hardening, structural steel. Упрочнение конструкционной стали с помощью многоканального СО 2 лазераЮгов В.И. Проведены исследования микроструктуры и распределения микротвердости образцов конструкционной стали марки 30ХН3А, упрочнённых лазерной закалкой с помощью непрерывного излучения многоканального (48 лучей) СО 2 -лазера на комплексе модели ЦЛТ-Ю-5. Для обеспечения равномерной структуры, твердости и глубины упроч-ненного слоя материала использовали лазерный излучатель с излучающими трубками, скомпонованными в виде пакета, состоящего из вложенных один внутри другого четырех восьмигранников (Patent RF № 2580350). Показа-на роль высокой степени однородности интегрального тепловложения по ширине полосы упрочнения на однород-ность свойств упрочненного слоя. Установлено, что в упрочненной зоне формируется структура мартенсит с тонким строением. Карбиды, входящие в состав исходной структуры сорбита, при лазерной закалке растворяются не пол-ностью. Они имеют глобулярную форму и размер 0,2…0,3 мкм. Микротвердость стали в упрочненной зоне около 6800 МПа. Равномерность глубины упрочненного слоя, которая характеризуется отношением минимальной глуби-ны упро...

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