Effect of sintering atmosphere on microstructure and properties of TiC based cermets

Abstract

The effect of the sintering atmospheres (vacuum, N₂, Ar) on the microstructures and properties of the TiC based cermets was studied using XRD, SEM/BSE and energy dispersive spectrometer. Compared with the alloy sintered in vacuum, the carbon content of the specimen sintered in N₂ and Ar is lower by 0.5%; and the nitrogen content is higher by 0.3% when sintered in nitrogen. The central part of the ring structure may be carbide with either a high W or Ti content. The ring structures are (Ti, W, Ta, Mo, Co, Ni)C solid solutions with different metallic elements and distributions. The composition of the binder phase is (Co, Ni) solid solution with different Ti, W, Ta, Mo, C contents. The structures are uniform for the cermets sintered in vacuum and the properties are the best. When sintered in Ar or N₂, the O₂ and N₂ in the atmosphere take part in the sintering reaction to break the carbon balance in the cermets to form a shell structure and defects, which results in poor density, microhardness (HV) and transverse rupture strength (TRS).

Keywords

TiC based cermets / sintering atmosphere / microstructure / mechanical properties

References

[1] TatsuzawaK., MatsubaraH., KiharaJ., IwamaK.. Preparation of TiC-Ni cermets using composite powders[J]. Journal of the Japan Society of Powder and Powder Metallurgy, 1990, 37(7): 1009-1012

[2] KinoshitaS., UekiM., SuzukiH.. Creep characteristics of TiC-Mo₂C-Ni cermet sintered after nitrification in the course of raising temperature[J]. Journal of the Japan Society of Powder and Powder Metallurgy, 1993, 40(8): 820-822

[3] TokumotoK., ShinoakiH., KitadaT., SakaguchiS.. Microstructures and mechanical properties of Ti-M-TiC(M:Cr,Mo,W) sintered hard alloy[J]. Journal of the Japan Society of Powder and Powder Metallurgy, 1994, 41(1): 27-32

[4] SabatelloS., FrageN., DarielM. P.. Graded TiC-based cermets[J]. Materials Science and Engineering A, 2000, 288(1): 12-18

[5] NomuraN., YoshimiK., KonnoT., HanadaS.. Fracture toughness improvement of TiC by Nb and Mo precipitates[J]. Journal of Materials Science Letters, 2000, 19(21): 1879-1881

[6] MatsubaraH., ShinS. G., SakumaT.. Growth of carbide particles in TiC-Ni and TiC-Mo₂C-Ni cermets during liquid phase sintering[J]. Materials Transactions JIM, 1991, 32(10): 951-956

[7] ChunD. I., KimD. Y., EunK. Y.. Microstructural evolution during the sintering of TiC-Mo-Ni cermets[J]. Journal of the American Ceramic Society, 1993, 76(8): 2049-2052

[8] YamamotoT., JaroenworaluckA., IkuharaY., SakumaT.. Nanoprobe analysis of core-rim structure of carbides in TiC-20wt%Mo2C-20wt%Ni cermet[J]. Journal of Materials Research, 1999, 14(11): 4129-4131

[9] ZaripovN. G., KabirovR. R., BloshenkoV. N.. Structural peculiarities of cermets design based on titanium carbide[J]. Journal of Materials Science, 1996, 31(19): 5227-5230

[10] ChoiK., ChoiJ. W., KimD. Y., HwangN. M.. Effect of coalescence on the grain coarsening during liquid-phase sintering of TaC-TiC-Ni cermets[J]. Acta Materialia, 2000, 48(12): 3125-3129

[11] LindahlP., RolanderU., AndrénH. Ō.. Atom-probe analysis of the binder phase in TiC-TiN-Mo2C-(Ni,Co) cermets[J]. International Journal of Refractory Metals and Hard Materials, 1993, 12(3): 115-119

[12] AndrénH. Ō., RolanderU., LindahlP.. Phase composition in cermeted carbides and cermets[J]. International Journal of Refractory Metals and Hard Materials, 1993, 12(3): 107-113

[13] KinoshitaS., UekiM., SuzukiH.. Cutting performance of titanium carbide based cermet nitrified during the course of sintering[J]. Journal of the Japan Society of Powder and Powder Metallurgy, 1994, 41(2): 152-155

[14] ZackrissonJ., RolanderU., WeinlG., AndrenH. O.. Microstructure of the surface zone in a heat-treat cermet material[J]. International Journal of Refractory Metals and Hard Materials, 1998, 16: 315-322

[15] EttmayerP., KolaskaH., DreyerK.. Effect of the sintering atmosphere on the properties of cermets[J]. Powder Metall Int, 1991, 23(4): 224-229

[16] CaoW.-b., LiJ.-t., GeC.-chun.. Design and fabrication of TiC-based symmetrically compositional functional graded materials[J]. Materials and Design, 2001, 22(1): 45-51