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The study involves in-situ synthesis of CrFeAlTi composite coating using laser micro-melting processing. The coating was successfully prepared by laser irradiating CrFeAlTi coating prepared by flame spraying on the China low activation martensitic (CLAM) steel substrate, and then Al2O3-TiO2 composite ceramic coating was synthesized by in-situ reaction on the surface of flame sprayed coating. The coating morphology, microstructure, phase composition, micro-hardness, dry sliding wear properties and corrosion resistance in liquid PbBi alloy were analyzed by stereomicroscope, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), micro-sclerometer, vertical universal friction wear testing machine and static PbBi corrosion test device, respectively. The test results show that the surface of Al2O3-TiO2 composite ceramic coating is smooth, and the microstructure of coating is both homogeneous and dense without defects such as crack, dimple and porosity, etc., a good metallurgical bonding between the composite ceramic coating and the substrate, and the interface is obvious. The phases of the coating surface are mainly composed of Al2O3, TiO2, (Al.948Cr.052)2O3, Fe2TiO5 and FeCr, etc. The coating shows a high average micro-hardness of approximately 1864.2HV0.2, which is about three times higher than that of the CLAM steel substrate, and presents gradient distribution with stable transition from the coating surface to the substrate. Comparing with the substrate, the coating presents excellent wear resistance. The wear mass loss of the coating is just one sixth of that of the substrate. Meanwhile, the coating exhibits the best corrosion resistance in the liquid PbBi.

In this study, the effect of different Ca additives (Ca(OH)2, CaO, and nano‐CaCO3) on the composition and microstructure of the fused BaZrO3 crucible were investigated, as well as their interaction with Ti2Ni alloy during vacuum induction melting. Results showed that the crucibles had the same phase compositions when the doping amounts of Ca additives were the same. Three kinds of Ca additives provided three different grain sizes of CaO precursors to participate in the solid solution reaction. When the doping amount of the Ca additive was 5.3 wt.%, the ZrO2 phase in the fused BaZrO3 was disappeared, and the CaZrO3 phase was founded. The composition of the crucibles doped with 7.7 wt.% Ca additives only consisted of Ba1‐xCaxZrO3 and CaZrO3 phase. The relative densities and erosion resistance of the crucibles were improved effectively with the increase of Ca additive content. Moreover, the crucible doped with 7.7 wt.% nano‐CaCO3 additive exhibited the highest density and the thinnest erosion layer. The Ba1‐xCaxZrO3 and CaZrO3 phases were dissolved by the alloy melt, according to the interaction analysis. In addition, the crucible doped with nano‐CaCO3 additive had a higher content of refractory element concentration in the alloy melts in comparision with the other two kinds of crucibles due to their higher number of pores. [ABSTRACT FROM AUTHOR]

To meet the demand for efficient and reliable copper and aluminum (Cu/Al) joints in refrigeration and electric power industries, interfacial reactions in 3003 Al/T2 Cu and 1035 Al/T2 Cu joints brazed by Zn-xAl (x ranged from 2–25 wt.%) filler metals and their effects on the mechanical properties of the joints were investigated. Microstructures and fracture surfaces were observed combining with composition analysis. For 3003 Al/Cu joints, bulk CuAl and CuAl2 intermetallic compound (IMC) formed in brazing seams, and a CuAl IMC layer formed at the Cu side interfaces. For 1035 Al/Cu joints, bulk CuAl2 IMC formed in brazing seams, and an Al4.2Cu3.2Zn0.7 IMC layer formed at the Cu side interfaces. For both kinds of joints, shear strength increased first, then decreased with the increasing Al content. The increase in shear strength was because Al promoted the formation of Cu-Al IMC, and caused dispersion strengthening. With the excessive Al content, however, the bulk IMC became coarse and the IMC layers at Cu side interfaces grew thick, causing the joint strength to decrease due to stress concentration. The strength of 3003 Al/Cu joints was always higher than that of 1035 Al/Cu, and their highest strength were achieved by Zn-12Al and Zn-15Al, respectively. [ABSTRACT FROM AUTHOR]

In this study, a type of red mud/slag-based cenospheres/geopolymer foam was directly fabricated using the direct foaming method at room temperature. The effects of high-temperature exposure (700–1100 °C) on the phase evolution, pore structure, and properties of the foams were investigated. The results showed that the untreated foam was amorphous structure. The porosity of the foams increased from 36.4 ± 0.6% (1 wt%) to 71.9 ± 0.1% (5 wt%) with the addition of H 2 O 2. The compressive strength of the foams was 1.20–18.15 MPa, which was attributed to the good bond between the cenospheres and red mud/slag-based geopolymer matrix, the fractured spheres, and the crack deflection. After this high-temperature exposure, the foam crystallized mainly into the leucite and mullite phases. The density and compressive strength of the foams decreased as the exposure temperature increased. The thermal conductivity of the foams reached the lowest value of 0.169 W/(m⋅K) and 0.108 W/(m⋅K) with 5 wt% H 2 O 2 before and after the exposure, respectively. These foams have demonstrated good potential for application in the building insulation field. [ABSTRACT FROM AUTHOR]

(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 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]

The optimized sintering conditions for a 3.5 wt% magnesia partially stabilized zirconia (Mg-PSZ) refractory were proposed in our recent research. The influence of the sintering temperature on the development of phase composition, microstructure, densification, thermal expansion and mechanical strength was studied in detail by X-ray diffraction (XRD), scanning electron microscope (SEM), He-pycnometer, high temperature dilatometry and three-point bending test. The samples sintered at 1670 °C had the highest bend strength, the maximum densification, the lowest thermal expansion coefficient (CTE), a homogeneous microstructure and a linear change in thermal expansion. [ABSTRACT FROM AUTHOR]

The effect of WC content on microstructure and mechanical properties of the TiC–Ni 3 Al system cermets was investigated. Ni 3 Al-bonded cermets showed a core–rim structure with carbide particle coupled with rim embedded in Ni 3 Al binder. With WC content increasing, TiC grains were refined and the white rim became complete and got thicker gradually. Interface between core and rim showed a completely coherent relationship. The rim enriched in W constituted an ideal coherence between hard phase and Ni 3 Al binder phase. With WC content increasing, the densification of cermets was enhanced, and hardness and TRS were increased firstly and then reduced, reaching peak values 90.9 HRA (HV 30 15 GPa) and 1629 MPa, respectively in cermet N5 (25 wt% WC). Similarly, fracture toughness got a peak value (11.6 MPa m 1/2 ), at the composition with 20 wt% WC. [ABSTRACT FROM AUTHOR]