Investigation of thermal oxidation resistance of nanopowders of refractory carbides and borides

Thermal oxidation resistance in air of nanopowders of carbides and borides of vanadium, titanium, chromium, and zirconium, as well as silicon carbide, is investigated. It is found that, at the temperature of onset of oxidation in air, they are arranged into the following series: carbides TiC (548 K), VC and Cr₃(C_0.80N_0.20)₂ (553 K), ZrC (560 K), and SiC (905–913 K), and borides VB₂ (620 K), TiB₂ (643 K), CrB₂ (763 K), and ZrB₂ (823 K). The results of investigation allow one to recommend nanopowders of carbides and borides for use as strengthening phases of composition coatings that operate in oxidizing media at temperatures no higher than the onset of oxidation. Nanopowders of chromium and zirconium borides and silicon carbide can be considered as equivalent substitutes for diamond nanopowders in composition coatings.     

Measurement of the abrasive capacity of powders of carbides and borides of refractory metals

Summary The abrasive capacity of carbides and borides of titanium, zirconium, hafnium, vanadium, chromium, tantalum, molybdenum, and tungsten was investigated.     

The wetting of refractory carbides,borides, and nitrides by molten metals

Summary The investigation has shown that the wetting of refractory compounds by metals is directly linked with the character of their chemical reaction, as well as with the direction of preferential transport of elements, from the melt to the refractory support or vice versa. The wetting of a support material by a melt can be controlled by means of additions to one of the contacting materials, which either intensify or weaken the transport of atoms participating in reaction, in the required direction.Translated from Poroshkovaya Metallurgiya, No. 7 (43), pp. 53–56, July, 1966.     

Porous materials from carbides and borides of the transition metals

Summary As a result of an investigation, procedures were developed for producing porous materials from carbides and borides of refractory metals by sintering freely poured spheroidized powders and precompacted blanks. Process parameters for the production of parts of the required porosity and permeability were determined. A study was made of the permeability of porous materials from carbides and borides of refractory metals.     

Self-lubeicating iron coatings containing oxides,carbides, and borides

Conclusions It is shown that the wear resistance of multicomponent composite coatings is higher than that of some quenched constructional, alloy, and tool steels.Translated from Poroshkovaya Metallurgiya, No. 2(182), pp. 26–29, February, 1978.     

The electrical properties of chromium borides,carbides, and nitrides

Summary The electrical properties of borides, carbides and nitrides of chromium were studied, which made it possible to elucidate certain questions of the electron structure of the given phases.It was established that for an atomic proportion of metalloid of 0.25 there is a quantitive correlation between the electrical resistance and the magnitude of its first ionization potential.The variation in the electrical properties with a rise in the metalloid content in the systems Cr-B, Cr-C and Cr-N is explained by the differences in the effects of atoms of boron, carbon and nitrogen on the value of the overlapping of 4s and 4p chromium bands, on the degree of its d-state defect, and also the difference in the ionization potentials of the indicated metalloids.     

感应软熔工艺对镀锡板耐蚀性的影响

采用电化学、酸蚀浸泡、表面形貌观察、微区成分分析等方法研究了感应软熔工艺条件(加热功率、软熔速度以及淬水温度)对镀锡钢板耐蚀性能的影响.结果表明,在恒定的软熔速度下软熔加热功率存在着最佳区域,软熔功率较高或较低时都会降低镀锡钢板的耐蚀性;在保证相同的软熔效果的前提下改变软熔工艺的加热时间,也会对镀锡钢板的耐蚀性产生影响,缩短软熔加热时间可以提高镀锡钢板的耐蚀性;软熔工艺中的淬水温度对镀锡板耐蚀性也有明显影响,淬水温度在30～40℃和80℃附近时可以得到良好的耐蚀效果.     

Effect of pulsed laser radiation on the microstructure of polycrystalline carbides and borides

Translated from Poroshkovaya Metallurgiya, No. 10(322), pp. 52–57, October, 1989.     

无金属粘结相硬质合金的电化学腐蚀行为

采用1 700℃、20 MPa高温高压固相烧结工艺制备WC-0.5Cr3C2-0.3VC、WC-3.65TiC-2.45TaC-0.47Cr3C2-0.28VC和WC-6Mo2C-0.47Cr3C2-0.28VC等3种无金属粘结相硬质合金。采用CHI 660C电化学工作站研究在pH=1的H2SO4溶液、pH=7的Na2SO4溶液和pH=13的NaOH溶液中3种合金的电化学腐蚀行为。结果表明,在pH=1的H2SO4溶液和pH=7的Na2SO4溶液中WC-6Mo2C-0.47Cr3C2-0.28VC合金的耐腐蚀性能最好,在pH=13的NaOH溶液中WC-3.65TiC-2.45TaC-0.47Cr3C2-0.28VC的耐腐蚀性能最好。3种无金属粘结相硬质合金在pH=13的NaOH溶液中的耐腐蚀性能均优于其在pH=1的H2SO4溶液中的耐腐蚀性能。综合比较合金的硬度、耐腐蚀性能以及原材料价格,3种合金中WC-6Mo2C-0.47Cr3C2-0.28VC合金具有更佳的性价比。     

Mechanical treatment of powders of refractory carbides

Conclusions The model of mechanical treatment constructed in this work makes it possible to reduce all the parameters of this treatment to three generalized parameters: the mean energies of movement of the spheres_s, particles _p, and the fraction of absorbed energy . The main input parameters of the conditions are the vibrational speed V_a = A and the flow of the powder qv.On the basis of calculations of the energy characteristics of mechanical treatment of the powders of the tantalum carbides and semicarbides we can estimate the contribution of mechanical energy of this treatment to the activation of the processes of synthesis of the semiand subcarbides of these metals. Specifically, the effect of synthesis of the refractory tantalum semicarbide directly in the chamber of the vibratory mill during mechanical treatment can be explained.Translated from Poroshkovaya Metallurgiya, No. 4(280), pp. 91–96, April, 1986.