INSTITUTE  OF  PULSE  PROCESSES  AND  TECHNOLOGIES

NATIONAL  ACADEMY  OF  SCIENCE  OF  UKRAINE
© 2012  Institute of pulse processes and technologies NAS of  Ukraine.
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| Institute's structures | Dept. No 43 | Obtaining the high-abrasion-resistant metal-matrix composites      
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TECHNOLOGICAL  METHODS  OF  OBTAINING 
THE  HIGH-ABRASION-RESISTANT METAL-MATRIX  COMPOSITES 
AND  DISPERSION-STRENGTHENED  NANOPARTICLES

Microelectronic photos of a mix of powders Fe-T³-B  C
                                                                                               4

X-ray diagram of a mix of micropowders Fe-T³-B  C
                                                                                        4
à (8000õ)
before treatment (d    ~ 80 μm)
                  cp
b (10000õ)
after HVED treatment (high-disperse mix of particles
d    ~ 0,7 μm, in which ~ 25 % of particles
                           cp
are < 0,3 μm  with ~ 15 % of particles < 0,1 μm)
à - before treatment,
b - after HVED treatment
ESSENCE OF TECHNOLOGICAL METHODS
Making of the high-abrasion-resistant dispersion-strengthened materials is based on possibility of an effective use of the state-f-the-art methods of
                                                                                                                                                                                                                -5          -7
high-concentration energy streams action on disperse systems - dispersion, activation, and synthesis of polydisperse micro- (10     to 10     m) and
                      -7          -9
nanosize (10     to 10    m) composite powders and the relatively low-temperature method of compaction - the  spark plasma sintering. Abiding to the
effects of necessary disperse phases initiation at the high-voltage electrodischarge (HVED) action on the elementary powders and their mixes it is
feasible to create the heterogeneity of the furnace charge and purposefully affect the growth rate of the grains by the high-rate method of spark plasma
sintering. Such technological methods allow for forming the fine-grained microheterogeneous structure with high physicomechanical properties - the
elevated strength (to 30 %) and wear resistance (to 60 %) of the parts operated in extreme conditions. The procedures and apparatuses for realization
of these methods are patented.
PURPOSE OF THE TECHNOLOGICAL METHODS
The technological methods are guided at obtaining of high-abrasion-resistant "carbide steel" composites and new composites with metallic bonds for the production of constructional and instrumental items operating in the conditions of friction and high loads, such as the parts of oil and gas pumps, the parts of metallurgical and mining equipment which are exposed to heavy wear (guiding rollers of wire rolling machines, etc.).
Essentially new compositions of high-abrasion-resistant dispersion-strengthened materials mainly produced from the available domestic raw-material base, in particular - iron and titan whose reserves are plenty in Ukraine are developed - the sound alternative to the exported raw materials, and also new highly effective technological approaches to obtain such materials with use of the up-to-date methods of synthesis of composite disperse powders of iron and titan carbides and borides by the high-voltage electrical discharges.

BENEFITS OF THE TECHNOLOGICAL METHODS
The enhanced strength and wear hardnesses of materials (by 30-60 % and more) is achieved by the technology when strengthening disperse particles are not inserted mechanically into a powder mix as the additional component like in the known methods, but they are separated as a result of reactionary electrodischarge synthesis at the HVED treatment of the elementary powders and their mixes in a hydrocarbonic fluid, which provides not only a high degree of dispersion, but also the essentially higher strength of the adhesive bond of strengthening microparticles and a base material.
Use of high heat-up rates and shorter holding time at the peak temperature during the spark plasma sintering of polydisperse micro- and nanosize composite powders allows obtaining the compacts with higher relative density and thinner structure compared with the use of traditional methods of sintering, such as hot pressing and hot isostatic pressing.

THE EXPERIMENTAL COMPLEX FOR THE SPARK PLASMA SINTERING
The specialists of IPPT of NASU developed the experimental complex for the spark plasma sintering called "Gefest-10" which is grounded on an immediate passing of target current with a peak value of 1 êÀ through a powder compound (AC and DC of the elevated frequency (10 kHz) superposition). The DC heats up uniformly the whole section of a compact, but the peripheral sites are cooled by the heatsink. The AC, owing to a skin-effect, is partially displaced to the section surface of the specimen and basically heats up the peripheral part. This compensates for the heatsink action and aligns the temperature conditions on the section.
The experimental complex "GEFEST-10" consists of the current source, the hand-operated hydraulic press ÏÐÃ-1, the vacuum chamber, the vacuum pump 2ÍÂÐ-5ÄÌ, and the control system. The current source is the spark-plasma sintering generator which consists of the power high-frequency rectifying transformer module, the high-frequency inverted rectifier with the air cooling system, drivers of transistors, and the control system.
The experimental
complex
for the spark plasma sintering
"Gefest-10"

The experimental complex for the spark plasma sintering "Gefest-10" contains the digital interface RS-485 to display on the PC the controllable parameters of temperature in the sintering domain, the current force passing through the sintered specimen, and voltage on the current carriers of the sintering chamber.
Basic technical characteristics
of the experimental complex
for the spark plasma sintering "Gefest-10"
Parameter
Min.
value
Max.
value
Output average power, W
-
12 000
Average output current, A
100
1 100
Output current amplitude, A
100
1 200
Output current modulation factor, %
0
50
AC component frequency, Hz
0
10 000
Output voltage, V
-
10
Microstructures of the consolidated material gained by spark plasma sintering
with use of the "Gefest-10" installation from powders after HVED treatment

à (5000õ)
b (5000õ)
carbide steel systems, the iron-carbon alloy - titan carbide (diboride), hardness of 68 HRC,
ultimate strength σ =1,350 MPa, porosity of 0.8 %
the iron-carbon alloy - titan carbide, hardness of 45 HRC, ultimate strength σ =650 MPa, porosity of 1,2 %
Basic technical characteristics
of the experimental complex
for the spark plasma sintering "Gefest-10"
Parameter
Min.
value
Max.
value
Temperature of sintering, °Ñ
-
1 600
Time of sintering, s
-
420
Pressure on the sintered blank, MPa
0,5
70
   
Pressure in the working chamber

(vacuum), Pa
     
     
   
10

        5
10
Diameter of specimen, mm
5
20
Sintering press stroke, mm
0,5
10
IMPLEMENTATION
The developed technological methods allow promoting the simplified technological scheme of obtaining the multipurpose materials dispersion-strengthened by nanoparticles applicable for the substantial increase of wear hardness and thermal stability of tools of different functions and constructional materials for reactor steels with enhanced properties of heat resistance, various motos, etc. to the market.
Simplified
technological scheme
of obtaining
the multipurpose
carbide steels dispersion-strengthened
by nanoparticles