Powders Of Refractory Compounds Research Articles

Shape, strength, and abrasive power of grains of refractory compound powders

Shape, strength, and abrasive power of grains of refractory compound powders

Grain geometry and strength of some refractory-compound powders

1. With increase in grain size, the value of mean rupturing load rises and that of specific strength falls. Arranged in order of increasing mean grain-rupturing load, the refractory compounds investigated form the following series: zirconium carbide, cubic boron nitride (BO), tungsten and aluminum borides, and silicon carbide. The results obtained may be utilized also at low machining speeds, under conditions approaching static loading. 2. The wide grain-strength range exhibited by various grades of synthetic diamond enables its high abrasive power to be utilized more fully. 3. In the grinding of titanium alloys, the least residual stresses are generated by abrasives exhibiting a relatively high microhardness, a low degree of chemical affinity for the work material, and a low grain strength.

Grinding and grading of micropowders of refractory compounds

1. The authors have determined the grinding time of the initial synthesized powders of refractory compounds so as to increase the yield of fine fractions during grading. 2. The use of a centrifuge with a water-jet pump accelerates the sedimentation of micropowders of refractory compounds and increases their size uniformity. The deposition times of micropowders and the weights of sedimentation samples have been calculated. 3. Methods of grading powders of different refractory compounds have been developed so as to obtain micro- and submicropowders.

Permeability of porous materials from refractory compounds

A study was made of porous materials from spheroidized powders of refractory compounds. A relationship is established linking permeability with porosity and the particle size of the powder from which the materials were prepared. An empirical formula is proposed for determining the dependence of the coefficient of permeability on powder particle size and component porosity under linear filtration conditions. The integral and differential pore radius distribution curves obtained show that such materials are relatively homoporous and exhibit little scatter in pore radius size.

Study of the densification of refractory compound powders by the electrical conductivity method

In this investigation, the electrical conductivity method was used for studying the compaction process of powders of titanium, zirconium, niobium, chromium, molybdenum, and tungsten carbides, titanium, zirconium, chromium, and tungsten borides, titanium and zirconium nitrides, and molybdenum and tungsten disilicides. In the pressure range investigated (5–75 kN/cm2), the densification process of the refractory compound powders is described by an exponential relationship between apparent electrical conductivity χ and relative volumeΒ. Following the example of [3], it is proposed that the degree of brittleness of refractory compounds be assessed from the tangent of the slope of the semilogarithmic straight line plot in In χ vsΒ coordinates, and tentative conclusions are drawn regarding the relative brittleness of the materials whose powders were compacted in this investigation.

The preparation and properties of spherical powders of refractory compounds

A study was made of the manufacture of spherical powders from refractory compounds by the method of granulating fine starting powders with a binder and subsequent sintering. Several physical and technological properties of spheroidized powders of refractory compounds were investigated.

Sintering of blanks obtained by die pressing powders of refractory compounds

This article describes an investigation of the process of sintering blanks made of refractory compounds by the die pressing method. The effect of the protective atmosphere of the furnace, containing CO, on the growth and shrinkage of samples during sintering is shown. It is found that one of the causes of the increase in size of MoSi2 and ZrB2 blanks at temperatures up to 1000‡C is the separation of free carbon from the gas phase on the grain boundaries.