Preliminary considerations

Direct Metal Laser Sintering (DMLS) is a net shape fabrication technology that has been developed especially to fulfill the requirements of rapid tooling. The most important factors for successful rapid tooling are: 1) accuracy, 2) surface quality, 3) material properties and 4) speed. Surface quality has been the major concern for development work because rapid tooling applications require very smooth surfaces and finishing work is often needed. The quality of all surfaces can be greatly improved by reducing layer thickness and adjusting optimal scanning parameters in the DMLS process. Simultaneously stair-stepping effect can be minimized and almost faded out. Straightforward progress to smaller layer thickness has required material development work of finer metal powders and intensive research work for optimal laser processing. Simultaneously part building strategies have become more intelligent. It has been proved in practical cases that even 20 µm thin layers can be used for building steel parts with superior surface quality.This paper describes some of the key features for Direct Metal Laser Sintering of very fine metal powders. Latest results and experiences of research and development team at Rapid Product Innovations (formerly Electrolux Rapid Development) are discussed.Direct Metal Laser Sintering (DMLS) is a net shape fabrication technology that has been developed especially to fulfill the requirements of rapid tooling. The most important factors for successful rapid tooling are: 1) accuracy, 2) surface quality, 3) material properties and 4) speed. Surface quality has been the major concern for development work because rapid tooling applications require very smooth surfaces and finishing work is often needed. The quality of all surfaces can be greatly improved by reducing layer thickness and adjusting optimal scanning parameters in the DMLS process. Simultaneously stair-stepping effect can be minimized and almost faded out. Straightforward progress to smaller layer thickness has required material development work of finer metal powders and intensive research work for optimal laser processing. Simultaneously part building strategies have become more intelligent. It has been proved in practical cases that even 20 µm thin layers can be used for building steel parts with s...

In this study, cupric oxide powder was prepared from copper powder using a thermal oxidation method. The copper powder was produced by electroless deposition method using ascorbic acid as a chemical reducing agent. The oxide powder product was synthesized at 500°C for 5 h. The metallic copper and oxide powder were characterized using X-ray diffraction and scanning electron microscopy. Based on results from these analytical techniques, it was determined that cupric oxide was successfully synthesized from the thermal treatment of copper powder and was in agglomerated state.

Aspects of Powder Technology in Ancient and Medieval India

Modeling and characterization of cohesion in fine metal powders with a focus on additive manufacturing process simulations

The electrical resistivity is an essential parameter describing materials’ capacity to convey electric current. Normal cementitious materials display high estimation of the electrical resistivity because of their insulating nature. However, the high electrical resistivity of concrete can be reduced by a sufficient amount of electrically conductive admixture. Such an improvement is advantageous in self-sensing or self-heating concrete design. In this study, the effects of metal additives on the electrical resistivity of hardening cement paste were investigated. In the experiments, two different types of metal admixtures; copper powder and iron powder were used. Hybrid composition of copper and iron were also considered for comparisons of the electrical resistivity. A water to binder ratio of 0.35 was used. The metal powders were used in the mixtures by replacing the cement in ratio of 0%, 5%, 10%, 15% and 20% by weight. The total binder content (cement and metal additives) was always the same in the experiments. The measurements were carried out at room temperature by using two-electrode- AC method. The test results indicate that the metal cement composites with 20% of cement weight improved the lower electrical resistivity of the cement paste than plain cement paste. In addition, composites with copper powders had less electrical resistivity than those with iron powders. The reduction of electrical resistivity with an increase of metal content was steady for when of using hybrid composites better than when using metal powders alone. The Different frequency options 1 kHz, 10 kHz and 100 kHz were used to investigate the effect of impedance-frequency and phase angle-frequency of a sample test using the LCR meter. The highest current frequency available on the LCR meter, 100 kHz, was chosen to be used as the applied current frequency in all of the experiments which exhibit much lower phase angle values that can cancel the effect of change in electrical resistivity measurements.

Purpose The purpose of this study is to optimize high-strength gears produced by powder metallurgical process and to provide a material model to predict the tooth root bending fatigue strength. Powder metal (PM) technology offers great opportunities for the reduction of the carbon footprint and improvement of the cost efficiency of gear production. PM gears can achieve flank load-carrying capacities comparable to wrought steel gears if the loaded volume is fully densified. Still, the tooth root strength is of particular importance. Design/methodology/approach The tooth root stresses can be minimized by optimizing the tooth root geometry. This usually leads to a target conflict, as fully optimized tooth root geometries cannot be manufactured by generating processes such as hobbing, generating-grinding or rolling. To use the increase in tooth root load-carrying capacity of fully optimized root geometry on PM gears, a non-generating method for surface densifying is needed. The shot-peening process is used as an alternative densification process for PM gears. The properties of both shot peened and cold-rolled PM gears are analyzed and compared. To quantify the effect of both manufacturing processes, the tooth root bending fatigue strength will be evaluated and compared to wrought gears. Findings From the fatigue strength perspective, a material model is developed, which is able to predict local endurable stress amplitudes. The model is gained through regression varying carbon content, density and size effect on bending specimens. Originality/value It is transferable to PM gears of the same material using a load transfer coefficient.

Well-established and new processes for the high-energy shaping of materials are analyzed along with the equipment they use. Most of the attention is given to the latest methods of high-energy compaction of metallic and nonmetallic powders on equipment made by the Swedish company Hydropulsor. Results are presented from studies performed on metal powders by scientists at the Swedish companies Hoganas and Sinterheat and Dalarna University, on powder ceramics (Al2O3) by French scientists, on copper and iron powders by Chinese scientists, and on carbon powders by the authors of the article.

Direct laser writing of aluminum and copper on glass surfaces from metal powder

It was demonstrated that highly porous sol-gel derived iron (III) oxide materials could be reduced to sub-micron-sized metallic iron by heating the materials to intermediate temperatures in a hydrogen atmosphere. Through a large number of experiments complete reduction of the sol-gel based materials was realized with a variety of hydrogen-based atmospheres (25-100% H{sub 2} in Ar, N{sub 2}, CO{sub 2}, or CO) at intermediate temperatures (350 C to 700 C). All of the resulting sol-gel-derived metallic iron powders were ignitable by thermal methods, however none were pyrophoric. For comparison several types of commercial micron sized iron oxides Fe2O3, and NANOCAT were also reduced under identical conditions. All resulting materials were characterized by thermal gravimetric analysis (TGA), differential thermal analysis (DTA), powder X-ray diffraction (PXRD), as well as scanning and transmission electron microscopies (SEM and TEM). In addition, the reduction of the iron oxide materials was monitored by TGA. In general the sol-gel materials were more rapidly reduced to metallic iron and the resulting iron powders had smaller particle sizes and were more easily oxidized than the metallic powders derived from the micron sized materials. The lack of pyrophoricity of the smaller fine metallic powders was unexpected and may in part be due to impurities in the materials that create a passivation layer on the iron. Several recommendations for future study directions on this project are detailed.

This paper considers a process of explosive compaction of detonation-produced nanodiamond powder together with nanopowders of metals to create composites. Use of particles of the nanodiamond having unique properties (hardness, heat conductivity, etc.) will allow obtaining of composite material with increased physical and mechanical properties. We considered powders of copper and aluminum as a metal matrix. As a result of theoretical consideration of the shockwave compaction for powder mixtures, we offered and discussed the conditions of explosive compaction. The compaction process can be characterized by a set of values of the shockwave pressure which define powder compaction, deformation, and particle heating. These values are: 1. minimum shockwave pressure under which the compaction and the shockwave in the powder do not occur; 2. pressure under which there is a jet cleaning of the particle surface; 3. pressure that will result in a homogeneous compact with maximum density; 4. pressure under which there is a phase transition of particles. Our research presents the result of calculations of the pressure thresholds for various powders of metals in mix with detonation-produced nanodiamond.

Applicability of fine industrial metallic iron-rich waste powders for hydrothermal production of hydrogen gas: The influence of non-ferrous contaminants

Ti42Zr40Ta3Si7.5Sn7.5metallic glass powder prepared for subsequent consolidation by hot pressing were produced by high energy ball milling from amorphous ribbon and both of the compositional and structural evolution on milled powders were studied using XRD and DSC analyses. By using WC vial and balls, the abrasion of milling media occurred causing WC contamination on < 105 µm milled powder after 2 cycles of milling. Based on DSC analysis, the contamination clearly reduced theΔTxof the alloy up to 48%. On the other hand, the contamination were overcome after milling using SS vial and balls, proved by no crystal peak observed on XRD pattern of all milling cycle levels. However, the thermal stability was noticed to be decreased implying the presence of nanocrystals on the amorphous powder after ball milling and the nanocrystal amount tend to be higher when more milling cycles were applied.

The production of metallic powder by precipitation from solution was studied in laboratory scale as an alternative to the conventionally adopted processes, based on the atomization of molten material, for producing metal powders with small particle size. The process is based on the precipitation of metals from aqueous solutions by reduction under controlled conditions. Results of laboratory scale experiments are presented for the production of copper particles from aqueous solutions of copper sulfate, using formaldehyde as reducing reactant, and EDTA as complexing agent. The effect of the presence of nuclei was studied. Metallic particles with average sizes in the range from about 0.3 µm to about 15 µm were obtained. In the process, large particles are formed mainly by aggregation of submicrometric particles, indicating that the particle size distribution of the product depends on the control of particle agglomeration rate.

Friction Stir Welding of Dissimilar Plastic-Based Material With Metal Powder Reinforcement

The present chapter mainly deals with several non-standard issues in the theory of plasticity for traditional metals as well as porous and powder metals. The flow formulation is adopted throughout the chapter. All the material models considered are rigid plastic, i.e. the elastic portion of the strain rate tensor is neglected. Assuming a rigid/perfectly plastic material model, it is shown that the velocity fields adjacent to surfaces of maximum friction must be describable by non-differentiable functions where the equivalent strain rate approaches infinity. This result is extended to the double-shearing model. Qualitative behavior of solutions based on various models of pressure-dependent plasticity is considered by means of problems permitting closed-form solutions. In particular, such features of the solutions as non-uniqueness, non-existence, singularity and rigid zones are emphasized. One possible application of the aforementioned singular solutions to describing intensive plastic deformation in a narrow layer near friction surfaces is shortly discussed.