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(Ti 1-x W x )C solid solutions (x = 0.05, 0.15, 0.25, 0.35) were synthesized by carbothermal reduction and then were used as hard phases to prepare (Ti,W)C-Ni 3 Al cermets by vacuum sintering. (Ti,W)C-Ni 3 Al cermets showed weak core-rim structure carbide particles embedded in Ni 3 Al binder. As W content in (Ti,W)C increased, core-rim structure of carbide particles got weaker and the contrast of particles lowered down in SEM-BSE morphologies. Furthermore, the densification of cermets was promoted with W content in solid solution increasing, meanwhile TRS and toughness of cermets were improved obviously. In this paper, the wettability of molten metal on different group transition metal carbides was discussed in detail based on valence-electron configurations (VECs) of carbides. [ABSTRACT FROM AUTHOR]

TiC–9.0TiN–19.5WC–0.5Cr 3 C 2 –0.3C–38.0(Ni– x Cr) ( x = 0, 10, 20 and 30 wt.%) cermets were prepared, to investigate microstructure and mechanical properties of Mo-free Ti(C,N)-based cermets with Ni– x Cr binders. 20–30 wt.% Cr in binders led to the obvious increase of the dissolution rate of WC, which was mainly attributed to the decease of the solid/liquid transition temperature of Ni-based binder phase. In the final microstructure, Ti(C,N) grains exhibited two kinds of the core/rim structure: one consisted of black core, white inner rim and grey outer rim, and the other consisted of white core and grey rim. Ti(C,N) grains with black core were on the whole larger in size, independently of Cr content in binders, and their grey outer rim increased in thickness with the increase of Cr content in binders. More often than not, white inner rims were thin and incomplete in shape, and there were fine white speckles in black cores, when Cr content in binders reached 20–30 wt.%. Lattice parameter of Ni-based binder phase increased with the increase of Cr content in binders, which was attributed to that the total amount of such alloying elements as Ti, W and Cr in this phase increased with the increase of Cr content in binders, and however, it increased slightly when Cr content in binders was in the range of 10–20 wt.%. Transverse rupture strength reached a peak value when Cr content in binders was 20 wt.%, and hardness increased with the increase of Cr content in binders. [ABSTRACT FROM AUTHOR]

Abstract The Ti-based composites reinforced by in-situ formed TiB and TiC particles were successfully produced by laser powder-bed fusion (LPBF) additive manufactured technology using a B 4 C/Ti composite powder mixture, in order to further enhance the mechanical properties of commercially pure titanium (CP-Ti). The effects of applied laser energy density on the microstructure and attendant mechanical properties of the LPBF-processed parts were investigated, and meanwhile, the underlying formation mechanisms of the TiB and TiC particles by LPBF were elucidated. It showed that the whisker-like TiB and near-granular TiC reinforcements were in-situ formed through a laser-induced reaction of Ti-B 4 C system via a diffusion-nucleation-growth mechanism from the melt. The in-situ reinforcements arranged from dendrite to cellular morphology were primarily determined by the thermal convections that transformed from dendrite to annular patterns as a result of the great elevation of temperature gradient between molten Ti liquid and heated B 4 C particles as an increase in the applied laser energy density. The tensile tests revealed that the LPBF-ed Ti-based composites possessed an enhanced tensile strength from 893 ± 5 MPa to 1211 ± 8 MPa and a slightly reduced elongation from 18.1% to 16.8% with the transition of typically fracture morphologies from elongated dimples to equiaxed-ultrafine dimples, respectively, attributed to the combined grain refinement and microstructure strengthening effects. Highlights • Ti-based composites with novel reinforcements were produced through laser powder-bed fusion. • Thermal convection induced by laser energy input is responsible for the arrangement of in-situ TiB-TiC reinforcements. • Composite with dendrite-shaped exhibits a low tensile strength in comparison to that with cellular one. [ABSTRACT FROM AUTHOR]

Abstract The present work investigated magnetic and mechanical properties of TiC– x TiN–15MC– y Ni (wt.%, MC = Mo 2 C, WC, x = 0, 3, 6, 9, 12, 15, and y = 20, 40) cermets. Room-temperature (RT) saturation magnetization M s of Mo 2 C-containing and WC-containing cermets decreased with increasing x , and that of Mo 2 C-containing cermets was lower at the same x and y. Ferromagnetism disappeared at RT for Mo 2 C-containing cermets regardless of x and y and for WC-containing cermets at x = 15 for y = 20 and x ≥ 12 for y = 40, mainly due to high total content of non-magnetic Mo (or W) and Ti in binder phase. At x = 15, Curie temperature T c of Mo 2 C-containing cermets decreased to about 97 K for y = 20 and 16 K for y = 40. For Mo 2 C-containing cermets, transverse rupture strength (TRS) and hardness reached the maximum at x = 6 for y = 20, and they increased with increasing x for y = 40. For WC-containing cermets, TRS reached the maximum at x = 6 whereas hardness decreased slowly with increasing x for y = 20, and TRS and hardness reached the maximum at x = 12 and 6 for y = 40, respectively. TRS and hardness of Mo 2 C-containing cermets were higher than those of WC-containing cermets at the same x and y , except x = 0, 15 for y = 20, mainly due to stronger ceramic grain refinement strengthening effect and stronger substitutional solid-solution strengthening effect of binder phase. Highlights • RT M s of cermets decreased with increasing TiN content, regardless of MC. • Ferromagnetism of cermets disappeared at RT for MC = Mo 2 C, regardless of x and y. • Ferromagnetism of cermets disappeared at RT for MC = WC at x = 15 for y = 20, 40. • For MC = Mo 2 C, T c of cermets decreased to ∼97 K for y = 20 and ∼16 K for y = 40. • TRS and hardness of cermets were generally higher for MC = Mo 2 C than for MC = WC. [ABSTRACT FROM AUTHOR]

Microstructure and shear strength of Ti(C,N)-based cermet/Cu 30Ag 3Ti filler metal/W9Mo3Cr4V steel joints were investigated after brazing in vacuum at 870, 910, and 950 °C for 20 min, and 910 °C for 10, 20, 30 and 40 min. The reaction layer of Cu Ni Ti solid solution between cermet and filler metal was difficult to form during brazing at 870 °C, leading to very low shear strength of joints. During brazing at 910 °C, Cu Ni Ti solid solution was formed between cermet and filler metal, and it became thick with the increase of holding time. Shear strength of joints reached a peak value for 30 min, due to the appropriate thickness of Cu Ni Ti solid solution. During brazing at 950 °C, Cu Ni Ti solid solution was formed and then grew on the whole along with Ag-based solid solution in filler metal, but was not formed between cermet and filler metal, thus deteriorating shear strength of joints. [ABSTRACT FROM AUTHOR]