CHANGE IN STRENGTH, HARDNESS AND CRACKING RESISTANCE IN TRANSITION FROM MEDIUM-GRAINED TO ULTRAFINE HARD ALLOY
https://doi.org/10.17073/1997-308X-2017-2-39-46
Abstract
The paper studies the microstructure and mechanical characteristics of samples of medium-grained (WC–8Co), submicron (WC– 8Co–1Cr3C2) and ultrafine (WC–8Co–0,4VC–0,4Cr3C2) hard alloys produced by liquid-phase sintering of powders of appropriate dispersity. The paper shows that a decrease in the average grain diameter from 1,65 to 0,37 μm leads to an increase in hardness of resulting alloys from 1356 to 1941 HV. At the same time, the cracking resistance decreases from 19,0 to 8,5 MPa·√ —m and strength decreases from 2080 MPa to 1210 MPa. Comparison with the literature data showed that alloys considered in this paper are highly competitive in hardness and crack resistance with analogues produced by sintering under pressure, hot pressing, electric spark and induction sintering. At the same time, the bending strength of alloys produced by liquid phase sintering was 1,5–2,5 times lower than for alloys produced by pressure sintering or pressing, due to the presence of pores with a maximum diameter estimated at 40 μm. The paper analyses obtained results and the literature data against the theoretical regularities. It is shown that in general, dependences of hardness, cracking resistance and strength on the average grain diameter of produced alloys and their analogues correspond to conventional regularities based on the Hall–Petch and Orovan–Griffiths laws, despite the existence of theoretical prerequisites for deviating from them.
About the Authors
M. I. Dvornik
Khabarovsk Scientific Center, Far Eastern Branch of Russian Academy of Sciences
Russian Federation
Cand. Sci. (Tech.), Senior researcher of Laboratory of composite materials
Russian Federation
Cand. Sci. (Tech.), Senior researcher of Laboratory of composite materials
A. V. Zaitsev
Khabarovsk Scientific Center, Far Eastern Branch of Russian Academy of Sciences
Russian Federation
Cand. Sci. (Tech.), Researcher of Laboratory of composite materials
Russian Federation
Cand. Sci. (Tech.), Researcher of Laboratory of composite materials
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For citations:
Dvornik M.I., Zaitsev A.V. CHANGE IN STRENGTH, HARDNESS AND CRACKING RESISTANCE IN TRANSITION FROM MEDIUM-GRAINED TO ULTRAFINE HARD ALLOY. Powder Metallurgy аnd Functional Coatings (Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional'nye Pokrytiya). 2017;(2):39-46. (In Russ.) https://doi.org/10.17073/1997-308X-2017-2-39-46
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