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A new design of the PTA torch (PTA torch) for surfacing of nickel, cobalt and iron-based alloys was developed. It combines two systems of powder feeding into the arc: the internal and external one. Such a combination expands the technological capabilities of the PTA torch, and allows surfacing magnetic and nonmagnetic materials. These systems can be used both separately from each other and together for surfacing composite alloys with separate feeding of the matrix and reinforcing powder material. In order to increase the efficiency of powder heating at external feeding into the PTA torch, an auxiliary stabilizing gas flow is used, which allows reducing the powder losses by 10-15 % and improving the deposited bead formation. Optimal flow rates of stabilizing gas are 4-5 l/min. The PTA torch effectively operates in the current range of 50-300 A. [ABSTRACT FROM AUTHOR]

Features of centrifugal plasma surfacing using powders of three different alloying systems based on iron and nickel were studied. It is found that at centrifugal plasma surfacing the iron-based test powder has the best welding-technological properties. It allows producing deposited metal of 200Kh15D2MS2R type. The layer deposited with this powder, has a microstructure of uniform height and ensures increase of the sleeve wear resistance 5-6 times, compared to batch-produced ones, which are made from steel 70 and "uenched by HFC. A design of the bushing component is proposed with replaceable surfaced sleeve, which is more adaptable to fabrication and allows repairing it by simple replacement of the worn sleeve. [ABSTRACT FROM AUTHOR]

Various combinations of separate feeding of cast spherical tungsten carbides and matrix alloy into the surfacing zone have been investigated. It has been established that when a self-fluxing nickel-based alloy is used as a matrix, the most stable surfacing process is achieved if tungsten carbides are fed through the axial bore in the focusing nozzle, and the matrix alloy comes through two channels located diametrically opposite to each other at its end. Ref. 6, 1 Table, 11 Figures. [ABSTRACT FROM AUTHOR]

The peculiarities of formation of a bead on narrow tip of screw flight in PTA surfacing were investigated. It is shown how a shape of deposited bead depends on its section and main technological parameters of surfacing, i.e. arc current, surfacing speed and PTA torch zenith displacement. The nomograms for selection of surfacing mode parameters were proposed. Equipment and consumables used for surfacing are also described. Repair of screws of extruders and automatic molding machines using PTA surfacing allows repairing these parts as well as 3-5 times increasing their service life in comparison with new nitrated screws. [ABSTRACT FROM AUTHOR]

The structure and properties of wear- and corrosion-resistant alloy of Fe-Cr-V-Mo-Ni-C system were investigated for plasma surfacing of screw conveyors of extruders and injection molding machines. It was shown that combination of high wear resistance and ductility of the alloy is achieved due to formation of a large amount of primary vanadium carbides VC and eutectics, located in the viscous austenitic-martensitic matrix in the form of single colonies. The alloy has an excellent formation and high resistance of the deposited bead to crack formation in surfacing, that allows surfacing rather massive parts without preheating. The service life of screw conveyors deposited using this alloy is 3-5 times higher than that of nitrated screws. [ABSTRACT FROM AUTHOR]

Area of investigation was powder losses in plasma-powder surfacing using plasmatrons with internal and external schemes of its feeding into arc. Dependence of powder losses on its fraction, geometry of deposited bead and surfacing efficiency was shown. It is determined that losses of powder from steel 10Kh18N10T are 4-5 times lower at internal scheme of feeding, due to its more effective heating in the arc than at external one and do not exceed 1-2 % under favorable conditions. Practical recommendations on efficient application of plasmatrons with different systems of powder feeding are given [ABSTRACT FROM AUTHOR]