Nickel Alloy Powder Research Articles

Plasma Spraying of Metal Coatings Using CO2-Based Gas Mixtures

Compared to argon, plasmas generated by molecular gases and operated at the same electric current level contain much higher enthalpy. This is because molecular gases must dissociate before ionization, which requires larger energy input. The authors have developed a new DC plasma torch, which operates with a mixture of carbon dioxide (CO2) and methane (CH4). The torch was employed for plasma spray coating with input power in a range of 30 to 45 kW. This paper reports on the effect of CO2/CH4 mixtures on the particle conditions during spraying of nickel alloy powders. Results of gas composition analysis at various distances from the nozzle exit are presented. The particle in-flight conditions, coating microstructure, and deposition efficiency are analyzed.

The influence of structural changes on electrical and magnetic characteristics of amorphous powder of the nixmoy alloy

Nickel and molybdenum alloy powder was electrodeposited on a titanium cathode from a NiSO4?7H2O and (NH4)6 Mo7O24?4H2O ammonium solution. The desired chemical composition, structure, size and shape of particles in the powder samples were achieved by an appropriate choice of electrolysis parameters (current density, composition and temperature of the solution, cathode material and electrolysis duration). Metal coatings form in the current density range 15 mA cm-2<j<30 mA cm-2. If the current density is greater than 40mA cm-2 then powders form. The chemical composition of powder samples depends on the current density of electrodeposition. The molybdenum content in the powder increases with the increase of current density (in the low current density range), while in the higher current density range the molybdenum content in the alloy decreases with the increase of the current density of deposition. Smaller sized particles form at higher current density. X-ray analysis, differential scanning calorimetric and measurements of the temperature dependence of electric resistance and magnetic permeability of the powder samples were all used to establish a predominantly amorphous structure of the powder samples formed at the current density of j?70mA cm-2. The crystalline particle content in the powder samples increases with the decrease of the current density of deposition. Powder heating causes structural changes. The process of thermal stabilization of nickel and molybdenum amorphous powders takes place in the temperature interval from 463K to 573K and causes a decrease in electrical resistance and increase in magnetic permeability. The crystallization temperature depends on the value of current density of powder electrodeposition. Powder formed at j=180 mA cm-2 begins to crystallize at 573K, while the powder deposited at j=50 mA cm-2 begins to crystallize at 673K. Crystallization of the powder causes a decrease in electric resistivity and magnetic permeability. The Curie temperature of the crystallized powders is about 10 K higher than the Curie temperature of amorphous powders.

Functional and Structural Characteristics of Metallic Foams Produced by the SlipReactionFoamSintering (SRFS)-Process

Highly porous open- cell materials on the base of various metals and alloys are of increasing interest as they combine structural and functional properties. There is a wide range of possible applications for such materials, e.g. as heat exchangers, filters or catalysts. A new and promising method to produce open- cell metallic foams on base of iron powder, low and high alloyed steel powders as well as nickel alloy powder is the SlipReactionFoamSintering (SRFS)- process. In comparison to other production processes of metallic foams, the SRFS- process provides several advantages: foaming at room temperature, allowing a very good process control by various parameters, foams of a great variety of metals are possible and a broad spectrum of properties is achievable.

Ｎｉ基合金粉末を用いた機械部品へのプラズマ肉盛及び高効率レーザ肉盛

The SUS316L stainless steel is widely used as the machinery parts for chemical plant and power plant. In order to improve the wear- and corrosion-resistance quality of parts, usually, the plasma process has been adopted to clad Co-based and Ni-based alloys powder on parts surface of SUS316L stainless steel. In the present work, the CO2 laser (2.4kW-CW) cladding of low residual stress and small distortion, and plasma cladding were investigated to deposit WELPC-6 Nickel alloy powder on the cylindrical prod for power plant. The smooth clad bead was obtained by CO2 laser cladding. The phases of clad layer were investigated by an optical microscope, scanning electron microscopy (SEM), X-ray diffractometer (XRD), electron probe microanalysis (EPMA), and energy-dispersion-spectrometer (EDS). The microstructures of clad layers belong to a hypereutectic structure. Primary phases consist of Cr7C3 and CrB. The eutectic structure consists of γ-(Ni, Fe)+Cr23C6 or γ-(Ni, Fe)+Cr2B. Comparing with the plasma process, the fine microstructures, low dilutions, and high Vickers hardness were obtained by CO2 laser cladding.

The correlation of processes of crystallization and changes of free electron density amorphous alloy powder Co80Ni20

Great attention is being given today to investigations on the capabilities and structural changes of amorphous and nanocrystal materials. Structural changes of the amorphous cobalt and nickel alloy powder obtained by electrochemical deposition were investigated in this paper. The crystallization process, as determined by the DSC method, occurred in two steps. The temperature dependence of electrical resistively and magnetic susceptibility in isothermal and non-isothermal conditions within the temperature range of room temperature to 700?C was determined for the powder samples pressed under pressure of 800 MPa. The X-ray structural examinations results correlate with those of the DSC analysis and the electrical resistively measuring.

Research on Direct Laser Sintering of Ni-Alloy Powder and Microstructure Feature

The direct laser metal sintering experiments were carried out with nickel alloy powder material system. The melting–solidification approach was discussed. Microstructure and components of DLMS-process sample were analyzed. The incomplete liquid phase sintering is the main mechanism of the melting-solidification approach. In powder material system, the additive copper improves the wettability of melting material, and minimizes the balling phenomenon. The equiaxial dendrite and the dendrite are the primary crystal morphologies. The compositions of materials are distributed uniformly.

Hydrogen Absorption and Desorption Kinetics in Nickel and Cobalt Alloy Powder

Hydrogen Absorption and Desorption Kinetics in Nickel and Cobalt Alloy Powder

The effect of temperature on structural changes of NI55CO45 amorphous powder

Cobalt and nickel alloy powders were obtained by electrochemical deposition on a titanium cathode from an ammonium solution of cobalt and nickel sulfate. Powders of a specific chemical structure and composition, particle shape and size were obtained by an appropriate choice of electrolysis parameters, current density, deposit growth rate and solution temperature and composition. Within the current density range of 5 - 450 mAcm-2, the current density did not significantly affect the chemical composition of the powders, but had a significant effect on the particle structure, shape and size. Crystal particles formed at a current density lower than 30 mAcm-2. Amorphous powders were obtained at a current density higher than 50 mAcm-2. Structural changes of the obtained amorphous powder of 55mol.% Ni, 45 mol.% Co, pressed under the pressure of 100 MPa, were investigated by measuring the temperature dependence of electrical resistance in isothermal and non-isothermal conditions varying from room temperature to 750?C. The process of thermal stabilization of defects that appeared during pressing occurred within the temperature range of 200-390?C. The DSC method was used to determine that the powder crystallization process occurred in two stages with peak temperatures of the exothermal maximum in the first and second stage of T1 = 438?C and T2 = 573?C, respectively. A distinct correlation between the change of electrical resistance and the crystallization process was established. The reduction of electrical resistively occurs during each crystallization stage.

The manufacturing of hard tools from metallic powders by selective laser melting

To make strong metallic parts directly from metallic powders, the selective laser melting method, in which metallic powders are successively melted and solidified in a microscopic zone, is proposed. From a series of tests on some metal powders, two types of solidified shapes are observed: successive balling and linear solidification. The second is suitable for the process. A nickel alloy powder used for cladding steel surfaces is found to be a good candidate for making dies. In making 3D shapes, deflection and cracking are caused in the product by rapid heating and quenching. To solve the problems, a dual laser scanning system in which YAG and CO 2 laser beams are offset a small amount from each other and scanned is proposed. From the results of three-point bending tests and Vickers hardness measurements on formed linear specimens, reheating by CO 2 after heating by YAG improves the material’s properties. It is considered that slow cooling or reheating after melting can eliminate residual stress and improve ductility.

パルス通電加圧焼結法による中空形状焼結体の作製

The ceramics(h-BN) core was applied for the Pulse Discharge Pressure Sintering (PDPS) method in order to consolidate the hollow shaped compact of the aluminum alloy powder(A 2014) and nickel alloy powder(Alloy 625).The densities of these compacts were 2.78 g/cm3 and 8.41 g/cm3, respectively. These values correspond to the densities of solid compacts which were sintered by PDPS without using the ceramic core.This method can be applied for the consolidation of complicated shape hollow compact like gear, tools etc, .

Behaviour of inert gas contamination in nickel alloy powder and consolidated compacts

Behaviour of inert gas contamination in nickel alloy powder and consolidated compacts

Behaviour of inert gas contamination in nickel alloy powder and consolidated compacts

Behaviour of inert gas contamination in nickel alloy powder and consolidated compacts

Kinetics of formation of interparticle contacts in the laser sintering of single component metallic powders

The joining of two spherical particles of nickel alloy powder under the action of lager irradiation, and the lager sintering of thin layers of poured powder were investigated. It was determined that powder particles experience surface melting under the action of lager heating, and join by a welding mechanism

Cavitation erosion of flame spray weld coating of nickel-base alloy powder

The cavitation erosion of flame spray weld coating of five kinds of commercial nickel alloy powder was investigated by using a vibratory cavitation apparatus. For comparison a plain carbon steel and a stainless steel were also studied. The result showed that the cavitation erosion resistance of the flame spray weld coating of the nickel alloys was strongly related to the degree of solution hardening of the matrix and the quantity, fineness and dispersivity of the second phase (compound).

Surface analysis of gas atomized nickel alloy powder and properties of compacted alloy : T. Fukuda et al (Sumitomo Metal Industries Ltd, Tokyo, Japan)

Surface analysis of gas atomized nickel alloy powder and properties of compacted alloy : T. Fukuda et al (Sumitomo Metal Industries Ltd, Tokyo, Japan)

The coelectrodeposition of raney nickel alloy powder on a stainless steel grid

Abstract A process for the coelectrodeposition of a Raney powder alloy on a stainless steel grid by a composite coating technique is described, along with grid surface preparation. Current density and total current passed were optimized as a function of percentage powder deposited on the steel grid.

メカニカルアロイング法により製造したニッケルアルミナイドの機械的性質

NiAl intermetallic compound, B2 type nickel-aluminide, is of particular interest because it combines good oxidation-resistance with a high melting point. In this study, NiAl alloys were produced by the mechanical alloying (MA) process for the purpose of refine-ment of microstructures. The MA was carried out in the attritor mill using pure nickel powder(4-7μm in diameter) and alloy powder (Ni-62.5at%Al, 43μm in average diameter) as starting materials. Mechanically alloyed powders were consolidated by the hot pressing. Changes of microstructures and mechanical properties during MA were investigated. MA proc-essing for longer periods produced the grain refinement and led to the formation of α-Al2O3 and Ni3Al phase in the NiAI matrix due to the oxidation of aluminum during MA. In the bending test for NiAl specimens produced under the condition of optimum MA processing time, the large deflection was obviously obtained above about 673K. Observing fracture surfaces, it was also found that the transition from a brittle cleavage fracture mode to a ductile fracture mode was caused by the application of the MA process even at the room temperature . These results are suggesting that MA process has good effect on the improvement of the ductility for NiAl.

Melting Phenomena of Several Nickel Base Alloys in a Plasma Jet Operating at Low Pressure

ABSTRACTThe modeling of powders melting in a plasma jet has received increasing attention as the plasma spraying is being developed to produce high density, high performance materials. These models are being used to predict process capability for melting powders and to develop plasma processing parameters for complete particle melting. Most models assume splherical powder particles which heat and melt uniformly during their travel in the plasma jet. The results of this research indicate this assumption may be invalid. Several experiments conducted to evaluate the melting behavior of nickel and nickel alloy powders (Ni,Ni2OCu, Ni2OCr, Ni5O Cr, Rene'80) are presented.

Experimental investigation of the process of powder manufacture by centrifugal atomization

A plant has been constructed, and a method developed, for the production of nickel alloy powders by centrifugal atomization of molten metal. A high-quality powder produced by this method was virtually free from gas pores in its <630-μm fraction and contained not more than 0.008 wt. % of oxygen.

Diffusion processes in the sintering of nickel alloy powders with spherical particles under pressure

Hot gasostatic pressing and subsequent annealing at 1200‡C result in the formation of 160–200-Μm diffusion zones between particles, which extend over practically the whole particle widths. During sintering under conditions of hot hydrostatic pressing, which is characterized by a shorter period of annealing at any given temperature and pressure, the widths of the diffusion zones after sintering and annealing attain 50–65Μm. The optimum diffusion zone width in the sintering of particles making good contact with one another (pure and even surfaces) is about 30–40Μm. However, the presence of oxides, carbide phases, and more complex compounds on the surfaces of particles substantially increases the optimum width of this zone. In such a case the optimum width is determined by the need for diffusion to cross interparticle contacts with diffusion-inhibiting barriers. In view of this, for particles of the nickel alloys investigated the optimum diffusion zone width may be taken to be ∼100Μm. At this width there are no areas in which the diffusion zone width is less than 40Μm, i.e., the minimum thickness at which strong bonds can be expected to form between particles.