Showing papers in "International Journal of Refractory Metals & Hard Materials in 2005"

Deposition, microstructure and properties of texture-controlled CVD α-Al2O3 coatings

Abstract: The influence of nucleation on the microstructure and properties of CVD Al2O3 was investigated. The experimental α-Al2O3 layers were deposited (a) without nucleation control and (b) with nucleation steps resulting in pronounced 〈101¯2〉, 〈101¯4〉 and 〈101¯0〉 growth textures. The experimental layers were characterised using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Wear properties of the textured coatings were evaluated in turning. The chemistry of the nucleation surface appeared to be an important factor in pre-determining the phase content and growth textures of the Al2O3 layers. Optimised nucleation resulted in substantially improved wear properties and these kinds of α-Al2O3 layers were typically composed of relatively small, defect-free grains exhibiting no porosity. The 〈101¯4〉 textured α-Al2O3 layer showed the best wear resistance.

The temperature ranges for maximum effectiveness of grain growth inhibitors in WC–Co alloys

Abstract: In order to more effectively control the WC grain growth during liquid phase sintering of submicron WC–Co alloys, the temperature ranges where common grain growth inhibitors are most active have been determined. In the study, small additions (0.5% by weight) of TiC, TaC, NbC, VC, and Cr3C2 were added to WC–6Co and WC–10Co alloys. In some cases, a small amount of coarse WC powder was added to simulate the effect of discontinuous grain growth. The powder compacts were vacuum sintered at temperatures ranging from 1300 to 1575 °C. The magnetic coercivity and microstructure results indicated that VC is equally effective in limiting continuous grain growth for all temperatures within the temperature range while the other inhibitors become more effective with temperature. VC was also found to be the most effective inhibitor of discontinuous grain growth. The results of the investigation are expressed in terms of the effectiveness of grain growth inhibition as determined by microstructural analysis, magnetic coercivity and hardness.

Correlation of transverse rupture strength of WC–Co with hardness

Abstract: The transverse rupture strength (TRS) of WC–Co composites is often loosely viewed as an equivalent of “toughness” which increases as hardness decreases in the industry The results of this study, conducted using a controlled group of WC–Co samples with consistent TRS values, suggest a different correlation between the TRS and hardness of WC–Co composites It was shown that TRS is closely related to the hardness and facture toughness Within a hardness range of 800

An experimental study of the sintering of nanocrystalline WC-Co powders

Abstract: Since nanocrystalline WC–Co powder was produced over a decade ago, the sintering of nanocrystalline powders remains a technological challenge. The goal of sintering nanocrystalline powders is not only to achieve full densification but also to retain nanocrystalline grain sizes. This is difficult because of rapid grain growth at high temperatures. Previous studies on the sintering of nanocrystalline WC–Co have shown that grains grow rapidly during the early stage of sintering. But there are few studies on the mechanisms of grain growth and densification during this stage. This paper presents the results of an experimental investigation on grain growth and densification of nanocrystalline WC–Co powders during heat-up at equilibrium solid-state temperatures. The results have shown that nanocrystalline WC grains grow rapidly during this period concurrently with rapid densification. The rapid densification and grain growth are partially attributed to the surface energy anisotropy of tungsten carbide. The effects of vanadium carbide on grain growth at solid state during heat-up are also discussed.

Liquid phase sintering of functionally graded WC–Co composites

Abstract: Functionally graded cemented tungsten carbide (WC–Co) is an example of functionally graded materials (FGM) in which mechanical properties are optimized by the presence of microstructural gradients such as cobalt gradient and grain size differences within the microstructure. In particular, a cobalt gradient is preferred. However, the manufacture of FGM WC–Co with a cobalt gradient is difficult because the flow of the liquid phase during liquid phase sintering (LPS) would eliminate any initial cobalt gradient built into the powder compacts. In this paper, different factors, which can be used to influence the migration of liquid during sintering, are investigated. These factors include gradients in grain size, carbon and cobalt content, and sintering time. It is shown that a difference in particle size may induce a step-wise profile of cobalt concentration. Initial carbon content differences, however, can be used to obtain a gradient of cobalt during sintering. The effects of these factors are explained based on the roles of capillary force and phase reactions.

Passivity and pseudopassivity of cemented carbides

Abstract: During corrosion of cemented carbides the binder phase is selectively dissolved from the material. After the binder has been dissolved into the solution the remaining tungsten carbide skeleton can not withstand a mechanical force any longer and these loose grains can be easily removed even by light abrasion. In principle Co-based cemented carbide does not passivate. However the potentiodynamic curve of the material shows a conventional anodic behavior. It exhibits critical potential and breakthrough potential. Since the current density of WC–Co cemented carbides after reaching critical potential is several orders of magnitude higher when compared to true passivity this phenomenon is called pseudopassive behavior. Some precipitations could be formed in pseudopassive region at the interface of intact cemented carbide and the skeleton but they are not stable and re-dissolve into the corrosive solution. Modification of the binder with chromium carbide addition improves corrosion resistance of cemented carbides significantly. Chromium acts as an alloying element and yields to a formation of a mixed Co–Cr oxide layer as shown by EF-TEM analysis. This oxide layer is considered as a true passive layer decreasing the rate of dissolution of the binder. Vanadium has been found to dissolve into the binder besides of forming thin layer between binder and WC grains. Vanadium in the binder also improves corrosion resistance of cemented carbide.

Solid-state properties of hot-pressed TiB2 ceramics

Abstract: Due to the increasing industrial interest in TiB2 the present work was accomplished to establish various solid-state properties of TiB2 and to study the influence of sintering aids and different powder conditioning methods on the densification behaviour of TiB2 The powders were hot-pressed in graphite dies with various loads up to 45 MPa and the vertex temperature of 1800 °C was held for 1 h For the pure, non-activated powders theoretical densities between 974% and 995% were obtained at a pressure of 45 MPa Hot-pressed activated powders at this pressure led to densities of up to 999% The addition of 05 wt% of various sintering aids also increased the densities It is shown that pre-alloying TiB2 with CrB2 is to favour over mixing the powders If TiB2 and the sintering aid were mixed the best result was obtained with Cr2N Ceramics with high Young’s moduli and hardnesses were obtained The Poisson’s ratios of two samples were 008 and 009, respectively, which are the lowest known values for a ceramic hard material The heat conductivity of pure TiB2 is approximately 1/4 of that of copper and the electrical resistivity is only 6 times higher than that of copper

Novel ultra-coarse hardmetal grades with reinforced binder for mining and construction

Abstract: Novel ultra-coarse WC–Co grades with a Co-based binder reinforced with nano-particles have been developed and implemented in industry on a large scale. The new grades with the brand name MASTER GRADES®, consist of rounded WC grains and the Co-based binder comprising nano-particles of the θ-phase (Co2W4C). The new hardmetal grades are characterised by a combination of higher hardness and transverse rupture strength as result of the binder hardening and reinforcement. Wear-resistance of the new grades in laboratory tests on abrasion, cutting of granite and abrasive concrete is found to be 2–3 times higher than that of standard grades with the same Co content and similar WC mean grain size. Life of mining and construction tools with the MASTER GRADES® is dramatically prolonged as a result of their enhanced wear-resistance and resistance to the initiation and propagation of thermal and fatigue cracks.

Laser processing of hardmetals: Physical basics and applications

Abstract: Laser material removal is an effective processing technique for hardmetals, which cannot be machined by chip-removal techniques. The basic physics of the laser–matter interactions and the influence of different laser parameters are discussed, with emphasis on sintered WC–Co specific features. The collateral affected zones and their occurrence mechanisms for laser machining with both nanosecond and femtosecond pulses are discussed. Experiments were carried out with pulsed laser systems operating in IR and UV, with ns and fs pulses and their results endorse the theoretical considerations. The use of direct or indirect laser processing (ns and fs pulses) in the surface engineering of coated/uncoated WC–Co parts is also presented. Subsequently, applications like laser microstructuring of tribological WC–Co surfaces and laser machining of integral chipbreakers are discussed.

Abrasive wear of WC–FeAl–B and WC–Ni3Al–B composites

Abstract: The abrasion resistance of WC–40vol%(FeAl–B), WC–40vol%(Ni 3 Al–B), and WC–40vol%Co, prepared from ultra fine precursor powders and processed by uniaxial hot pressing, has been investigated using a pin-on-drum tester. Intermetallic binders, with different amount of boron including 0, 250, 500, 750, and 1000 ppm B, were prepared in ultrafine form under controlled atmosphere using ring grinding, blended with submicron (0.8 μm) WC powder and then uniaxially hot pressed at 1500 °C under a pressure of 20 MPa for 4 min in 10 −2 MPa argon atmosphere. In an additional investigation, wear results were compared with that of commercial H10F (WC–10wt%Co, WC particle size of 0.7 μm). It was found that the wear resistance of WC–FeAl–B and WC–Ni 3 Al–B increased with the increasing amount of boron. WC–40vol%FeAl–B showed the highest abrasion resistance, close to that for WC–10wt%Co (H10F) composite, followed by WC–40vol%Ni 3 Al–B and WC–40vol%Co.

Influence of titanium nitride addition on the microstructure and mechanical properties of TiC-based cermets

Abstract: In this paper, the TiC-based cermets with addition of TiN were fabricated by a conventional powder metallurgy process. The titanium nitride (TiN) and titanium carbide (TiC) used as starting powders have been synthesized by the self-propagating high temperature synthesis (SHS) method. This exothermic reaction, easy to process, allows to obtain fine and original powders from low-cost raw materials. Cermets obtained by sintering powders of TiC and Mo2C with nickel binder phase are investigated. The effect of TiN adding on the microstructure and the mechanical properties of these composites are studied. Microstructures have been observed by scanning electron microscopy (SEM). Room temperature mechanical properties such as Young’s modulus, fracture toughness and microhardness have been measured and related to morphology and chemical composition of the samples. Tribological experiments were also performed and the friction coefficient of a cermet containing titanium nitride was compared with that of other hard materials. The SHS starting powders used present some particularities, as it was shown in a previous study [Materiaux a base de carbures et nitrures, pour coupe et usure, obtenus a partir de poudre SHS, PhD Thesis, INSA Lyon, 2004]. The purpose of this work is to show that results concerning the impact of TiN addition on microstructure and mechanical properties obtained on bulk specimens, from these original starting powders, are similar to the ones obtained on alloys from commercial starting powders.

Infrared brazing Ti–6Al–4V and Mo using the Ti–15Cu–15Ni braze alloy

Abstract: Brazing Ti–6Al–4V and Mo using the Ti–15Cu–15Ni alloy has been extensively evaluated in the study. Both infrared and conventional furnace brazing are included in the experiment. Ti–15Cu–15Ni braze alloy demonstrates excellent wettability on Ti–6Al–4V at 970 °C. In contrast, the wettability of the molten braze on the Mo substrate is significantly improved for the test temperature above 1000 °C. The brazed specimen is primarily comprised of the Ti-rich phase, and there is no interfacial reaction layer observed in the joint. Most of the brazed joints are fractured at the Mo substrate except for the joint infrared brazed at 970 °C for 180 s. For the specimen infrared brazed at 970 °C for 180 s demonstrates the average shear strength of 251 MPa, and quasi-cleavage fracture with sliding marks on facets is widely observed in the fractured surface. ABAQUS® stress simulations are also performed in order to illustrate the effect of residual stresses in the brazed joint during shear test. Based on the simulated result, there are two possible fracture locations in the brazed joint due to the presence of high Mises stresses, i.e., the braze alloy and Mo substrate. Additionally, the inherent low strength of the Mo substrate results in premature failure of the brazed joint during shear test for most brazed specimens.

Strength predictions for bulk structures fabricated from nanoscale tungsten powders

Abstract: In concept, nanoscale tungsten powders should enable the production of very hard, strong, and wear-resistant sintered tungsten alloys and compounds. However, data from the press-sinter processing of small tungsten powders generally do not provide the anticipated property gains. Accordingly, existing press-sinter data from a range of tungsten particle sizes are used to formulate a model relevant to nanoscale powders. The model includes both size-dependent and temperature-dependent aspects. Available data are used to train the model to allow calculations of the sintered strength for various powders and processing cycles. Model predictions for density, grain size, sintered hardness, and sintered strength are used to isolate new processing strategies customized to nanoscale powders. Preservation of the nanoscale microstructure requires considerable departure from standard powder handling practices and fabrication cycles.

Application of a wax-based binder in PIM of WC–TiC–Co cemented carbides

Abstract: A wax-based binder was developed for powder injection molding of WC–TiC–Co cemented carbides. The critical powder loading and the rheologic behavior of the feedstock were determined. It was found that the critical powder loading could achieve up to 62.5 vol% and the feedstock exhibited a pseudo-plastic flow behavior. The injection molding, debinding and sintering processes were studied. The dimensional deviation of the sintered samples could be controlled in the range of ±0.2% with the optimized processing parameters. The mechanical properties were better than or equivalent to those of the same alloy made by the conventional press-sintering process.

Characterization and wear behavior of modified silicon nitride

Abstract: Silicon nitride-based materials are applied to many tribological components because of their superior thermal and mechanical properties and corrosion resistance. The purpose of this study is to investigate the wear performance of modified silicon nitride which contained 3 wt.% La 2 O 3 and 3 wt.% Y 2 O 3 . The relationships between microstructure and mechanical properties have been also addressed. Vickers microhardness and toughness were measured, the later being determined by means of the direct crack measurement method (DCM). Scanning electron microscopy technique (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) was used for the morphological characterization of the samples as well as for the characterization of the wear scars. Wear properties were studied under a load of 10 N by using the ball-on-disk tribometer. AISI 52100 steel balls and balls of WC + 6% Co (6 mm diameter) were used as static counterparts, respectively. Steady state friction coefficients of 0.66 and 0.62 were measured for the tribological pairs WC + 6 % Co/Si 3 N 4 and AISI 52100/Si 3 N 4 , respectively. The wear mechanism was determined in each case, and comparison between the wear performance of the traditional and modified silicon nitride is also presented.

Compression behavior of TaC0.98 under nonhydrostatic and quasi-hydrostatic pressures up to 76 GPa

Abstract: Powder samples of TaC0.98 sandwiched between aluminum disks were placed in a rhenium gasket and compressed in a diamond anvil cell. The X-ray diffraction patterns were recorded under pressures up to 50 GPa using synchrotron radiation. The presence of aluminum in the cell rendered the sample pressure nearly hydrostatic and also served as the pressure standard. In another set experiments,TaC0.98 powder mixed with small quantity of platinum powder was placed in stainless steel gasket and compressed between the anvils. The X-ray diffraction patterns were recorded up to 76 GPa. In absence of any pressure-transmitting medium, the stress state of the sample was expected to be highly nonhydrostatic. The diffraction data were analyzed using lattice strain theory to estimate, the difference between the axial and radial stress components in the sample. The magnitudes of t suggest that the lower limit13; of compressive strength of TaC0.98 increases with increasing pressure and reaches -11 GPa at 76 GPa pressure. No phase transformation was observed up to the highest pressure. The bulk modulus and its pressure derivative derived from the volume-compression-pressure data are 345(9) GPa and 4.0(4), respectively.

Quantitative microstructure analysis of tungsten heavy alloys (W–Ni–Cu) during initial stage liquid phase sintering

Abstract: Microstructure analysis plays an important role in studying liquid phase sintering process. In the current study, quantitative microstructure analysis was performed on tungsten heavy alloys with different Ni:Cu ratios using an advanced image analysis system. The measured microstructural parameters include grain size, neck size, pore size, porosity, connectivity, contiguity, neck size ratio, mean curvature and more importantly, their statistical distributions. Various statistical distribution functions were used to fit the measured data, and the model parameters were obtained. The effect of alloy composition and the corresponding effective sintering time on microstructure was discussed. The analysis results are important for studying the fundamental mechanisms of sintering, modeling and predicting liquid phase sintering process.

Environmental effects on friction and wear of dry sliding zirconia and alumina ceramics doped with copper oxide

Abstract: The influence of the addition of copper oxide on the friction and wear characteristics of dry sliding zirconia and alumina at various humidities and elevated temperatures is outlined in this article. At various humidities, it is found that the addition of CuO give a significant contribution in reducing the coefficient of friction of dry sliding zirconia against alumina (from 0.65 to 0.25) and alumina against alumina (from 0.55 to 0.35) systems. At elevated temperatures, zirconia and alumina doped with CuO exhibit high friction (f > 0.6). The experiments reveal that alumina doped with CuO exhibit superior resistance to wear even at high temperature.

Mapping the compaction and sintering response of tungsten-based materials into the nanoscale size range

Abstract: Considerable knowledge exists on processing tungsten powders over a broad particle size range. Published data and processing models have been combined for tungsten powders ranging from 20 nm to 18 μm to build a response model for press-sinter processing. The model predicts apparent density, green density, green strength, sintered density, sintered grain size, and product properties such as strength, hardness, and wear resistance. Further, the model isolates several problems as particle size decreases that will require changes in how tungsten powders are handled, compacted, and sintered. Maps of strength versus processing conditions are generated from the model to direct future efforts toward improved properties using nanoscale tungsten powders. From these findings, new opportunities become evident for press-sinter consolidation of nanoscale powders.

Processing and properties of ZrO2(3Y2O3)–Al2O3 nanocomposites

Abstract: Nanocomposites of yttria-stabilized zirconia (YSZ), containing 20 and 40 wt% alumina, were prepared by a two-step process: (1) fine-particle aggregates of the constituent phases were melted and homogenized in a high enthalpy plasma, prior to rapid quenching in water to obtain metastable starting powders, and (2) the metastable powders were consolidated by hot isostatic pressing (HIP), under conditions designed to ensure the formation of nanocomposites by controlling the metastable-to-stable phase transformation during sintering. In both cases, the resulting nanocomposites had completely uniform structures, comprising 27 and 50 vol% of α-Al 2 O 3 in a tetragonal YSZ matrix phase. Measurements of hardness and indentation toughness were correlated with observed structures.

Study of solid-state sintered fine-grained cemented carbides

Abstract: Submicron cemented carbides are most often produced by liquid phase sintering. To retard the grain growth during sintering, these materials are sintered at low temperatures and with addition of grain growth inhibitors, e.g. Cr and V. The common hypothesis is that the sintered material would benefit from a more evenly distributed inhibitor in the WC raw material, in order to control the grain growth during both the solid-state and liquid phase part of the sintering. Aiming to study the distribution of Cr specifically after solid-state sintering, a Cr-doped WC-powder was mixed with Co and excess of carbon, and subsequently hot-pressed for 1 h and 30 MPa at 1200 °C. This transmission electron microscopy study shows that Cr is concentrated to the surfaces of the WC grains in the sample after mentioned solid-state sintering.

HIP after sintering of ultrafine WC-Co hardmetals

Abstract: This paper analyses the changes induced by HIP after sintering on the microstructure and mechanical properties of WC–7wt.%Co ultrafine hardmetal grade. The well known correlation between porosity reduction and fracture strength improvement is confirmed in these compositions, this being more effective at HIP temperatures above the eutectic point of the alloy. In absence of GGI, hardness decreases continuously as the HIP temperature increases. However, for specimens containing VC and Cr 3 C 2 additions, hardness increases as the HIP temperature increases from 1200 °C to 1400 °C. This anomalous trend, confirmed by WC grain size observations, could be related to the activation of coalescence mechanisms during solid state HIPing, which are inhibited by the presence of a liquid phase.

Grain size softening in nanocrystalline TiN

Abstract: The effect of grain size d on the hardness H of TiN is considered, with focus on the nanometer grain size range H increases from ∼22 GPa to ∼32 GPa with decrease in d from single crystals to d = 50 nm Three sets of data show that H decreases with further reduction in d below 50 nm, ie, grain size softening occurs The softening is not in complete or unequivocal accord with any of the three models normally proposed for such softening, namely Coble creep, grain boundary shear and dislocation line tension modification Factors which could have contributed to the softening are: (a) changes in texture and in turn the corresponding value of the Taylor orientation factor M and (b) the presence of weakening imperfections produced during fabrication

Bulk titanium nitride material obtained from SHS starting powder: Densification, mechanical characterization and tribological approach

Abstract: Powders used for this study were synthesized by the self-propagating high temperature synthesis (SHS) process. This method allows producing titanium nitride powders in an economic and easy way. Densification of these original powders is carried out by the hot pressing process. Sintering is achieved, under a 50 MPa pressure, at different temperatures (1400 °C, 1600 °C and 1800 °C). At 1600 °C properties are optimised and bulk specimen density is superior to 98%. In addition, microhardness reaches the average value of 1790 ± 225 HV and Young modulus measured is 430 ± 10 GPa. A tribological characterization is then carried out with an adapted four balls machine tribometer. Titanium nitride tribological behavior is compared with the one of other hard materials such as 100C6 steel, titanium carbide and two cemented carbides of different compositions. Parameters such as toughness, hardness and wear volume are correlated in order to understand wear mechanisms origins.

Sintering shrinkage of WC-Co materials with different compositions

Abstract: The composition of cemented carbides affects not only the properties of the finished product, but also changes the sintering behaviour. In this work the sintering of medium-coarse WC-Co materials has been investigated. Descriptions of the constitutive behaviour, uniaxial viscosity, viscous Poisson's ratio and sintering stress, obtained from dilatometry experiments under uniaxial load were extended to cover different material compositions. The proposed models were used to express the linear shrinkage rate, and the model parameters fitted to shrinkage data from materials with different carbide grain size, cobalt content and carbon content. The influence of grain size distribution was also investigated. Finally, the shrinkage rate was used to numerically integrate for sintering shrinkage under different thermal cycles.

Indentation hardness of biomorphic SiC

Abstract: Vickers hardness (HV) measurements have been performed in SiC samples fabricated from various wood precursors (pine, beech, and eucalyptus): bioSiC. It was found that hardness was highly dependent on starting wood structure. The arrangement of wood cells determined the final microstructure of the bioSiC (pores distribution and SiC/Si ratio). Two well-differentiated regions could be observed in all samples; a fully dense area corresponding to the wood growth rings and another that was mostly porous (porosity volume fraction between 30% and 50%). Indents in dense regions revealed that hardness increased with decreasing SiC/Si ratio. Hardness values were compared with those of commercial reaction-bonded SiC and hot-pressed SiC. HV values in the porous region could be well described using a Ryskevitch-type equation.

Machining of hot pressed alumina-boron carbide composite cutting tool

Abstract: Al 2 O 3 –B 4 C composites containing up to 40 vol.% of dispersed B 4 C particles were fabricated by hot-pressing and machined as cutting tools. This composite showed higher micro-hardness and toughness than monolithic Al 2 O 3 because of the restricted grain growth by the presence of hard B 4 C particles. Machining tests were conducted on a carbon steel work piece to evaluate the performance of the Al 2 O 3 –B 4 C cutting tool.

Microcrack formation in plasma sprayed thermal barrier coatings

Abstract: Air plasma sprayed ZrO2–8wt%Y2O3 thermal barrier coatings were deposited under tightly controlled conditions. The lengths and orientations of the horizontal cracks and vertical cracks in these coatings were characterized in detail, and process/structure maps of the crack distribution as a function of particle and substrate states were constructed. A fully coupled thermo-mechanical finite element model was used to study the buildup of stresses during splat solidification, and to understand the effect of deposition conditions on crack formation during plasma spray deposition. The model also showed that surface roughness plays a key role in determining the magnitude of maximum stresses, and that only roughness features on the scale of splat thickness are important in providing locations of maximum stress concentration.

On the thermal characterization of a HPHT sintered WC–15% wt Co hardmetal alloy

Abstract: Hardmetal is usually processed by the conventional powder technology techniques: mix of WC + Co powders, compacting, and liquid phase sintering. A new method to process hardmetal parts is hereby described. Parts of WC–15% wt Co were processed by using high pressure high temperature sintering (HPHT). The pressure of 5 GPa, temperature of 1350 °C, and time of 2 min of sintering was used. Results are shown as a function of micro-structure, densification, and hardness measurements. The open photoacoustic cell technique (OPC) was carried out in order to measure the thermal diffusivity of the hardmetal. In addition, heat capacity was considered and the thermal conductivity calculated. Results matched with the values of the literature where other photoacoustic techniques have been employed.

Infrared brazing of Mo using the 70Au-22Ni-8Pd alloy

Abstract: Infrared brazing of Mo using the 70Au–22Ni–8Pd braze alloy is performed in the experiment. Both Au-rich and Ni-rich phases are observed in the infrared brazed joint at 1050 °C. The Au in the molten braze is not reacted with the Mo substrate, but the Ni in the braze preferentially reacts with the Mo. With increasing the brazing temperature and/or time, the interfacial reaction between the molten braze and Mo substrate is greatly enhanced, and the angular MoNi intermetallic compound is formed in the brazed joint, especially for the furnace brazed specimen due to its slow thermal history. The formation of interfacial MoNi intermetallic compound in the brazed joint is detrimental to its bonding strength. Cleavage dominated fracture is widely observed from the fractograph of furnace brazed specimen. Additionally, the application of rapid infrared brazing is a very effective process to inhibit excessive growth of the interfacial MoNi phase in the joint.