Hot forging of P/M TiC reinforced and high speed steels
|Gennadii A. Bagliuk , Dmitro Goncharuk|
Institute for Problems in Materias Science (IPMS), 3, Krzhizhanivsky Str., Kiev 03680, Ukraine
Hot forging of porous preforms is the alternative method for manufacturing of piece preforms from tool steels powders in relation to liquid phase sintering, providing, at the same time, possibility for production of materials fine-grained structure which is approximating to characteristics of powder steels, produced by technology of hot isostatic pressing at solid-phase temperature interval with the subsequent hot hammering and (or) rolling.
Among the variety of wearproof iron based materials which are produced by methods of powder metallurgy, the carbide reinforced steels - composites on the basis of, as a rule, alloyed steels with disperse inclusions of transitive metals carbides particles (mainly – titanium carbide) with their mass composition from 15 to 70 % to take up special position.
The research of the basic technological parameters influence on structure features of hot forged materials produced from high speed steel – TiC powders mixture was the purpose of the present work.
Technological process for production of TiC reinforced steels with application of hot forging technology included following basic operations: miling of high speed steel and 20 % (weights.) titanium carbide powders mixture, compaction of porous preforms at pressure of 500 MPa, its heating in argon to temperature 1150 ¸1160 0С and hot forging in a closed matrix on a crank press.
Comparative analysis of produced by liquid phase sintering or hot forged composites microstructures has shown, that in a structure of sintered material the TiC grains, settling down mainly on borders of matrix grains, create rather coarse-dispersion grid structure. The average size of TiC grains makes about 1,8 microns, and matrix grains - 13 microns. Application of hot forging, practically not changing the average size of TiC grains (about 1,7 microns), at the same time allows to crush essentially alloy matrix structure which sizes of grains decrease in 2 ¸ 2,5 times.
The effect of alloy formation activation is found out at hot plastic working in high speed steel – titanium carbide powder system. Quality standard of elements distribution between matrix and titanium carbide particles has shown, that in a composites, produced by liquid phase sintering, TiC grains are enriched by vanadium, tungsten and molybdenum with distinctly expressed circular-type structure on grain borders. In a case of application hot forging technology, the concentration of elements is substantially equalized, therefore essentially more uniform distribution of alloying elements across the field of microsection is observed.
Presentation: Oral at E-MRS Fall Meeting 2009, Symposium I, by Gennadii A. Bagliuk
See On-line Journal of E-MRS Fall Meeting 2009
Submitted: 2009-05-24 12:17 Revised: 2009-06-07 00:48
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