Abstract
Electro-explosive alloying as a method of pulse-plasma treatment consists in accumulation of energy by a battery of pulsed capacitors and its subsequent discharge for 100 μs through a conductor in form of titanium foil with silicon carbide powder, while conductor is under explosive destruction. Method of electro-explosive alloying of tungsten-cobalt hard alloy includes melting of surface and its saturation with explosion products, followed by self-hardening by removing heat deep into the material and environment. On the surface of VK10KS hard alloy, the coating was obtained with thickness of up to 15 – 20 microns with nanohardness of 26,000 MPa. Using X-ray phase analysis and scanning electron microscopy, it has been established that new phases of TiC, W2C, (W, Ti)C1 – x , WSi2 with high hardness were formed in the surface layer. As a result, friction coefficient decreased to 0.18 compared to the initial 0.41. Investigations with transmission electron microscopy have revealed changes during electro-explosive alloying that occur in surface carbide and near-surface cobalt phases. Dislocations accumulations were found in the carbide phase. In cobalt binder, deformation bands (slip bands), single dislocations, and finely dispersed precipitates of tungsten carbides were revealed. This change can be explained by stabilization of cubic modification of cobalt, crystal lattice of which has a large number of slip planes upon deformation and greater ability to harden in comparison with hexagonal modification of cobalt. Additional alloying with cobalt binder in heat affected zone after pulse-plasma treatment have a positive effect on the service life of tungsten-cobalt hard alloys as a whole due to their stabilization.
Highlights
Using X-ray phase analysis and scanning electron microscopy, it has been established that new phases of TiC, W2C, (W, Ti)C1 – x, WSi2 with high hardness were formed in the surface layer
Investigations with transmission electron microscopy have revealed changes during electro-explosive alloying that occur in surface carbide and near-surface cobalt phases
Zhang F.G. Dry sliding wear mechanism of WC-13Ni hard alloy irradiated by high-intensity pulsed electron beam // Tribology Letters
Summary
Способ ЭВЛ заключается в формировании структуры и изменении свойств металлов и сплавов при импульсном воздействии на поверхность многофазной плазменной струей, сформированной из продуктов электрического взрыва проводников. Источником теплового воздействия и легирующих элементов при ЭВЛ на поверхность является импульсная многофазная плазменная струя, сформированная из материала взрываемого проводника. Это позв оляет предположить, что ЭВЛ проводников с дополнительной навеской карбида кремния приведет к дополнительному легированию кобальтовой связующей поверхностного упрочненного слоя кремнием и, тем самым, продлится эксплуатационный срок изделий. Исследование структуры твердого сплава после электровзрывной обработки осуществляли с помощью растровых микроскопов «Philips SEM 515», «Philips XL-30» и просвечивающего электронного микроскопа марки Tecnai 20 G2 TWIN фирмы FEI (Нидерланды) с ускоряющим напряжением 200 кВ. Результаты измерения нанотвердости представлены как среднеарифметические значения, полученные от 10 испытаний на трех образцах после обработки с помощью компьютерной программы Mountains Map Universal, версия 2.0.13. Трибологические испытания образцов в спеченном состоянии и после многокомпонентной электровзрывной обработки проводили с помощью высокотемпературного трибометра «PC-Operated High Temperature Tribometer» при комнатной температуре. Профилометрические исследования проводили на установке «Micro Measure 3D station» фирмы CSEM
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