Plasmatron for Coatings

The paper analyzes reasons for application of plasma torches of special design for deposition of heat-resistant layers of thermal barrier coatings that contribute to minimum oxygen content in the zone of spraying. It contains detailed description of design for a plasma torch with a nozzle that allows better protection of a plasma stream against atmospheric exposure.Heated inert gas (Ar) is fed inside the nozzle along its walls through holes in its end part. Air around a plasma jet is displaced, additional compression of the plasma occurs and due to this oxygen content is decreased in a coating and efficiency of material deposition is increased. An additional use of a tungsten insert in an electronic node makes it possible to create a pair of tungsten – tungsten in an electrode assembly and the life of the electrode assembly will be increased due to high erosion resistance, electrical conductivity, thermal conductivity and sufficient strength in 2–2.5 times while increasing spray performance through toughening regimes. The paper presents testing results of the developed plasma torch and its prototype for duration of continuous operation and intensity at 500 A current, 70 V voltage, nitrogen flow rate of 45 l/min (standard mode for deposition of oxide ceramics). Coatings from nickel–chromium–aluminum–yttrium powder have been obtained while using plasma torches with the same parameters of deposition and a comparative analysis of the technological properties have been made in the paper. The developed plasma torch has more qualitative characteristics of subsurface plasma coatings: increase in adhesive strength – by 1.4 times, material utilization ratio – by 1.3 times, micro-hardness – by 1.3 times, porosity decrease – by 2.3 times.

Solution to Technological Problems of Raising the Reliability and Quality of Castings Based on Titanium Alloys

We consider the problems of the complex application of the aluminium-yttrium binder in the fabrication of high-temperature resistant melting crucibles and investment molds thermoschemically resistant to titanium melts. The results of the contact interaction investigations of a molten titanium alloy with a material of aluminum-yttrium ceramics are presented. The usage of ceramic products of α-Al2O3–Y3Al5O12∙α-Al2O3 composition under conditions of high-temperature melting and pouring under vacuum minimizes the physicochemical interaction and significantly reduces the alpha case layer on cast products, thereby improving their operational properties.