Effects of nano TiN addition on the microstructure and mechanical properties of TiC based steel bonded carbides

TiC based steel bonded carbides with the addition of nano TiN were prepared by vacuum sintering techniques.The microstructure was investigated using scanning electron microscopy（SEM） and transmission electron microscopy（TEM）,and the mechanical properties,such as bending strength,impact toughness,hardness,and density,were measured.The results indicate that the grain size becomes small and there is uniformity in the steel bonded carbide with nano addition;several smaller carbide particles are also found to be inlaid in the rim of the larger carbide grains and prevent the coalescence of TiC grains.The smaller and larger carbide grains joint firmly,and then the reduction of the average size of the grains leads to the increase in the mechanical properties of the steel bonded carbides with nano addition.But the mechanical properties do not increase monotonously with an increase in nano addition.When the nano TiN addition accounts for 6-8 wt.% of the amount of steel bonded carbides,the mechanical properties reach the maximum values and then decrease with further increase in nano TiN addition.

Microstructure of reactive synthesis TiC/Cr18Ni8 stainless steel bonded carbides

TiC/Crl8Ni8 steel bonded carbides were synthesized by vacuum sintering with mixed powders of iron, ferrotitanium, ferrochromium, colloidal graphite and nickel as raw materials. The microstructure and microhardness of the steel bonded carbides were analyzed by scanning electron microscope （SEM）, X-ray diffraction （XRD） and Rockwell hardometer. Results show that the phases of steel bonded carbides mainly consist of TiC and Fe-Cr-Ni solid solution. The synthesized TiC particles are fine. Most of them are not more than 1 μm. With the increase of sintering temperature, the porosity of TiC/Crl8Ni8 steel bonded carbides decreases and the density and hardness increase, but the size of TiC particles slightly increases. Under the same sintering conditions, the density and hardness of steel bonded carbides with C/Ti atomic ratio 0. 9 are higher than those with C/Ti atomic ratio 1.0. The TiC particles with C/Ti atomic ratio 0. 9 are much finer and more homogeneous.

Modeling and optimizing of steel and mushy Al-28Pb alloy bonding

The bonding of steel and mushy Al 28Pb alloy was studied. The relationship model about preheat temperature of steel plate, solid fraction of mushy Al 28Pb alloy, rolling speed and interfacial shear strength of the bonding plate was established by artificial neural network perfectly. This model can be optimized by a genetic algorithm, and the optimum bonding parameters for the largest interfacial shear strength are: 546 ℃ for preheat temperature of steel plate, 43.5% for solid fraction of mushy Al 28Pb alloy and 8.6 mm/s for rolling speed, and the corresponding largest interfacial shear strength of bonding plate is 70.3 MPa. [

Semi-solid Processing of Steel-Al-7 Graphite Binding Plate

The bonding of steel plate to Al 7graphite slurry was studied for the first time. The relationship model about preheat temperature of steel plate,solid fraction of Al 7graphite slurry, rolling speed and interfacial shear strength of bonding plate could be established by artificial neural networks perfectly.This model could be optimized with a genetic algorithm.The optimum bonding parameters are:516℃ for preheat temperature of steel plate,32.5% for solid fraction of Al 7graphite slurry and 12mm/s for rolling speed,and the largest interfacial shear strength of bonding plate is 70.6MPa.

Diffusion bonding between nickel－base superalloy K24 and heat－resisting steel 1Cr11Ni2W2MoV

The Vacuum diffusion bonding between nickel-base superalloy K24 and heatresisting steel 1Cr11Ni2W2MoV was studied and the effects of welding parameters,including bonding temperature T,pressure P,time t,vacuum V and interlayer thickness h ,on the microstructure and properties of the joint were investigated.The optimum parameters for the diffusion bonding were found to be:T=1100￣1200℃,t=5￣30 MPa,V≥1×10-2 Pa.When the welded specimens are tensioned at room temperature,ductile fracture takes place at the nickel-base superalloy part or at the joint and the tensile strength reaches 850 MPa,When the tensile tests are carried out at 500℃ ,all the bonded specimens fractured at heat-resisting steel part,and tensile strength is 750 MPa.The interlayer thickness greatly affects the joint properties,and the interlayer thickness depends on the size of the bonded specimen.The impeller of nickel-base superalloy K24 and shaft of heat-resisting steel 1Cr11Ni2MoV,which are used in aerospace engine,has been successfully jointed jointed by means of high frequency induction diffusion bonding.

The Bonding Properties of Solid Steel to Liquid Aluminum

The bonding of solid steel plate to liquid al uminum was studied using rapid solidification. The relationship models of interf acial shear strength and thickness of interfacial layer of bonding plate vs bond ing parameters (such as preheat temperature of steel plate, temperature of alumi num liquid and bonding time) were respectively established by artificial neural networks perfectly.The bonding parameters for the largest interfacial shear stre ngth were optimized with genetic algorithm successfully. They are 226℃ for preh eating temperature of steel plate, 723℃ for temperature of aluminum liquid and 15.8s for bonding time, and the largest interfacial shear strength of bonding pl ate is 71.6 MPa . Under these conditions, the corresponding reasonable thickne ss of interfacial layer (10.8μm) is gotten using the relationship model establi shed by artificial neural networks.

Thickness of compound layer in steel-aluminum solid to liquid bonding

The bonding of solid steel plate to liquid aluminum was studied using rapidsolidification. The surface of solid steel plate was defatted, descaled, immersed (in K_2ZrF_6 fluxaqueous solution) and stoved. In order to determine the thickness of Fe-Al compound layer at theinterface of steel-aluminum solid to liquid bonding under rapid solidification, the interface ofbonding plate was investigated by SEM (Scanning Electron Microscope) experiment. The relationshipbetween bonding parameters (such as preheat temperature of steel plate, temperature of aluminumliquid and bonding time) and thickness of Fe-Al compound layer at the interface was established byartificial neural networks (ANN) perfectly. The maximum of relative error between the output and thedesired output of the ANN is only 5.4%. From the bonding parameters for the largest interfacialshear strength of bonding plate (226℃ for preheat temperature of steel plate, 723℃ for temperatureof aluminum liquid and 15.8 s for bonding time), the reasonable thickness of Fe-Al compound layer10.8 μm was got.

Detailed Evolution Mechanism of Interfacial Void Morphology in Diffusion Bonding

Similar diffusion bonding of 1Cr11Ni2W2MoV stainless steel was conducted at different bonding tem- peratures. The interface characteristics and mechanical properties of joints were examined, and the evolution of interracial void morphology was analyzed in detail The results showed that there were four typical interfacial void shapes generating sequentially： the large scraggly voids, penny-shaped voids, ellipse voids and rounded voids. The variation of interracial void shape was dominated by surface diffusion, while the reduction of void volume was ascribed to the combined effects of plastic flow of materials around voids, interface diffusion and volume diffusion. Owing to the elimination of void from the bonding interface, the sound joint obtained could exhibit nearly full interracial contact, and present excellent mechanical properties, in which the microhardness and shear strength of joint matched those of base material.

Study of bond strength between various grade of Ordinary Portland Cement(OPC)and Portland Pozzolane Cement(PPC)mixes and different diameter of TMT bars by using pullout test

Since last two decades,the Portland Pozzolane Cement(PPC)is extensively used in structural concrete.But,till to date,a few literature is available on bond strength of concrete using PPC mixes.There are many literatures available on bond strength of concrete mixes using Ordinary Portland Cement(OPC).Hence,a comparative study was conducted on bond strength between OPC and PPC mixes.In the present investigation,total 24 samples consisting of M20,M35 and M50 grades of concrete and 16 and 25 mm diameter of TMT bar were tested for 7 and 28 days.The pullout bond test was conducted on each specimen as per IS:2770-1967/1997[1]and the results were observed at 0.25 mm slip at loaded end called as critical bond stress and at maximum bond load called as maximum bond stress.It was observed that the critical bond strength of PPC mixes is 10%higher than OPC mixes.Whereas,marginal improvement was noticed in maximum bond strength of PPC mixes.Hence,based on these findings,it could be concluded that development length for PPC mixes could be reduced by 10%as compared with same grade of OPC mixes.