CC BY
32ÏSHS2019
Moscow, Russia
APPLICATION OF HARDMETAL ELECTRODE MATERIALS IN PULSED ELECTROSPARK DEPOSITION TECHNOLOGY
T. G. Penyashki*", M. I. Petrzhik0, and A. E. Kudryashov0
aISSAPP "N. Pushkarov" - Agricultural Academy, Sofia, 1331 Bulgaria bNational University of Science and Technology MISiS, Moscow, 119049 Russia
*e-mail: [email protected]
DOI: 10.24411/9999-0014A-2019-10120
Electrospark deposition (ESD) technology is widely used in various industries due to the excellent performance and high adhesion of the formed coatings, the possibility of local processing of large products, the relative ease of implementation and automation capabilities. The coating process is environmentally friendly and low energy consumption. Traditionally, metals and their alloys, graphite, as well as WC-containing hard alloys of VK (WC-Co), TK (TiC-WC-Co), TTK (TiC-WC-TaC-Co) grades, obtained by powder metallurgy technology, are used as electrode materials in ESD technology.
However, microcrystalline WC-containing hard alloys do not always meet the requirements for electrode materials, due to their high erosion resistance, low transfer coefficient, and high cost. In this connection, there is an urgent need to create economical electrode materials from tungsten-free hard alloys. The aim of the work is to demonstrate the advantages of tungsten-free electrode materials compared to standard hard metal alloys.
Currently, non-tungsten electrode materials have been developed, which are successfully used in many industries. Depending on the technical problem to be solved, electrode materials are selected that form multifunctional coatings on the surface of the processed products: wear-resistant, heat-resistant, corrosion-resistant, antifriction, with increased hardness, etc. To improve the performance properties of coatings, additives affecting erosion resistance are introduced into the materials. The compositions of electrode materials used to strengthen the cutting tool of high-speed steel HS6-5-2 are shown in Table 1 [1].
Table 1. Compositions of tungsten-free electrode materials for hardening the cutting tool.
Grade of electrode materials_Composition
TNM10 TiC + 10% Ni + Mo
TN10 TiN + 10% Ni + Cr
KNT16 TiCN + 16% Ni + Mo
TNM20 TiN + 20% Ni + Cr
TC TiC + 14% Ni, Mo + 1% Cu, B, AhOs
TN TiN + 14% Ni, Cr + 1% Cu, B, AhOs
TC-TN TiC + TiN + 12% Ni, Mo + 1% Cu, B, AhOs
It is found that the resource of tools hardened with tungsten-free alloys (countersinks, cutters) more than 2.5 times exceeds the resource of non-hardened tools and 1.2-1.5 times the resource of tools treated with WC-Co electrodes. The best properties have the coating formed with TC-TN electrode.
To strengthen the rolling rolls made of white cast iron SPKhN-60 by the ESD the tungsten-free electrodes manufactured by technology SHS were tested [2]. The compositions of the studied electrode materials are given in Table 2.
XV International Symposium on Self-Propagating High-Temperature Synthesis
Table 2. The compositions of electrode materials for strengthening rolling rolls.
No. Grade of electrode materials Composition
1 SHIM *- 40HA TiC-40 % NiAl
2 SHIM - 9/20A TiB-20 % Al
3 SHIM - 11 TiB2-40 % NiAl
4 SHIM - 20H TiC-20 % Ni
5 SHIM - 2/40HM TiC-40 % (Mo-70% Ni)
6 BK6 WC-6 % Co
7 T15K6 15 % TiC-79 % WC-6 % Co
*Russian alloy grade "SHIM" (synthetic hard instrumental material).
Coatings deposited using SHS-electrode materials SHIM-11 and SHIM-40HA were characterized by higher performance properties (heat resistance, wear resistance) compared with coatings of deposited with tungsten-containing electrodes.
During industrial test at Oskol Electrometallurgical Plant it was established that electrospark deposition with SHS-electrode SHIM-40HA increases the resistance of the mill rolls more than 2 times. These materials were recommended for electrospark treatment of rolling rolls made of white cast iron in order to increase their operating time.
A new promising direction of development of electrospark alloying technology is the selection and application of metallic glass-forming precursor electrode materials, which form at ESD nanostructured coatings with high performance properties [3-6].
Developing this approach, the metallic glass (MG) containing surface layer has been formed on the metallic (Fe-based and Ti-based) substrates using glass forming precursors-electrodes having both high and low Glass Forming Ability (GFA). High GFA electrodes like Fe61Co7Zr10Mo5W2B15 and Fe48Cr15Mo14Y2C15B6 had pronounced supercooled liquid range (about 60 and 38 K, respectively). However, industrial amorphous Fe78Mo2B20 ribbon with lower GFA also was successfully applied as a precursor-electrode at ESD to form nanocrystlline and metallic glass contaned layer on titanium substrate. In this case, supercooled liquid range is missing and GFA is much lower comparing to the best glass formers [6]. So, it was found that the efficiency of heat removal of motionless substrate at ESD is comparable with that at quenching the melt by spinning on a rotating drum (cooling rate of about 1,000,000 K/s).
Surface glass formation is accompained by hardening of the crystalline metal substrate. It is achieved through a rapid local melting and solidification due to increasing of carbon and boron concentration and quenching stresses at near surface layers. This ensures high hardness (more than 15 GPa) and wear resistance (by three orders of magnitude) [3, 6]. Further development of this approach is associated with a reasonable selection for specific applications the certain couples "MG precursor-crystal substrate" as well as modes of electro spark deposition.
The present work includes studies funded by the Bulgarian National Science Fund (BNSF) of the Ministry of Education and Science under the project "Research and Development of New Wear-Resistant Coatings Using Compositional and Nano Materials" and by BNSF and Russian Foundation for Basic Research (RFBR) under the project no. 19-58-18022.
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3. M.I. Petrzhik, P.V. Vakaev, T.R. Chueva, et al, From bulk metallic glasses to amorphous metallic coatings, J. Metastable Nanocryst. Mater., 2005, vol. 24-25, pp. 101-104.
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4. E.A. Levashov, A.E. Kudryashov, E.I. Zamulaeva, et al, New classes of electrode materials for electrospark deposition, Proc. Int. conf. "Materials Science of refractory compounds: achievements and problems", 2008, Kiev, Ukraine, NASU, p. 162 (in Russ.).
5. A.V. Kolomeichenko, I.S. Kuznetsov, T.G. Penyashki, et al, On making problem of amorphous and nanocrystalline structures in electrical discharge coatings, Remont, Vosstanovlenie, Modernizatsiya (Repair, Reconditioning, Modernization), 2015, no. 5, p. 33 (in Russ.).
6. M. Petrzhik, V Molokanov, E. Levashov, On conditions of bulk and surface glass formation of metallic alloys, J. Alloys Compd., 2017, vol. 707, pp. 68-72.
