Silicon carbide heaters of the KEN B type (GOST 16139-70), as is well known, are made from a batch containing 98-98.5% SiC and 1.5-2% carbon black and undergo direct electrical firing in a siliconizing charge at 2000-2200~The formation of the structure of heater occurs mainly as the result of the sublimation--condensation and recrystallization of SiC via the gas phase.One of the important shortcomings of this type is the fairly high concentration of free silicon which frequently causes the negative sign of the temperature coefficient of the electrical resistance and lowers the working life of the heater [i].The Patents literature contains proposals for increasing the durability of the heaters by adding to the batch high-melting metals of Groups IV-VI and VIII of the Periodic Table (e.g., Ti, Mo, Cr, Fe, Co, or Ni) or compounds of these metals (carbides, borides and silicides).* However, there is no information on the effect these additions might have on the structure formation of the heaters and on their properties.The present paper deals with a study of the effect of additions of Co, Cr, Ni, and Mo on the structure formation, and properties of heaters of the KEN B type.Specimens 16 mm in diameter and 320 mm long were prepared from a batch containing 99% green silicon carbide (70% KZ No. 5; 9% KZ No. i0; and 20% KZ No. 4) plus 1% carbon black; the materials were vibrocompressed from the semidry masses and subjected to direct siliconizing firing using the processes described in [i]. To the initial batch composition we added 3% (on 100%) of finely dispersed (finer than 60 ~m) metal with a 99.5-99.8% concentration of the main component.After firing we determined the open porosity, the apparent density, the ultimate bend strength, and stability in still air at a temperature of 1600~ at the surface of the heaters with a specific load of 20 W/cm 2. The phase composition and the structure were studied using chemical, x-ray, and microscopic analyses.The results of the study are given in Table I. The addition of the metal leads to a 1.5-3% reduction in weight after the heaters have been fired, i.e., the metal has a beneficial effect on the sublimation--condensation process of the silicon carbide.According to the result~ of the chemical and metallographic analyses, the specimens without any additions contain a small quantity of silica after sintering: 0.4 and 1% of silicon. With the addition of metals there is no silica present in the specimens after firing and the concentration of free silicon is 0.3%.During the firing process, the cobalt and nickel are partially evaporated and what remains of them forms CoSi2 and NiSi2 along the grain boundaries of SiC. These processes affect the evaporation of silicon carbide and its recrystallization: the sintering of the heaters and the growth of SiC crystals clearly occurs not only via the gas phase but also through the liquid phase.It is well known that when SiC single crystals are grown, cobalt, and particularly chromium silicides promote the growth of large crystals of silicon ca...