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X-ray pure yttrium diborodicarbide (YB 2 C 2) was synthesized for the first time via modified spark plasma sintering (SPS) using Y 2 O 3 , B 4 C, and carbon as starting materials. Homogeneous intermixing of the raw powder by high energy ball milling (HEBM) promoted the formation of YB 2 C 2 powder with layered structure by boro/ carbo-thermal reduction. The average particle size of the synthesized powder at an optimum synthesis temperature (1625℃) was 568 nm. Small amount of YB 2 C was formed by consuming YB 4 at and above 1625°C. The metal basis purity of the synthesized YB 2 C 2 powder was 99.84%. X-ray pure YB 2 C 2 was obtained by densifying the synthesized YB 2 C 2 powder at 1900°C for 60 minutes at a pressure of 80 MPa using SPS. This study reports a simple method for the fabrication of X-ray pure rare earth metal diborodicarbides (ReB 2 C 2). K E Y W O R D S high energy ball milling, powder, spark plasma sintering, yttrium diborodicarbides 1230 | NGUYEN Et al.

In this work, to assess the possibility of obtaining an alloyed layer by plasma heating of the mixture of the PRV-BrO10 alloy and the coating of the welding electrode OK 84.78. The study of the structure is given using the optical microscope MET-2 and the measurement of microhardness -hardness testers of the HMV-G series. It is established that with a thin layer of pre-coating, the coatings are completely saturated, and with a thick layer -the formed zones are different in microstructure and microhardness. In the case of 0.25 mm precoating thickness, the addition of chromium carbide leads the strong increasing of the hardness compared to tin-bronze alone. In the case of 0.50 mm pre-coating thickness, for the upper soft zone rich in copper, the average microhardness value is below 250 HV, and for hard particles in this zone in the range of 500-700 HV, the lower saturated zones have high hardness in a wide range . The slow scanning speed of the torch and a thick layer of pre-coating are the reason for incomplete saturation and the appearance of defects on the surface of St3 steel.