Electroslag additive manufacturing: A pathway for high throughput near net shape production

Development of a computer-aided concurrent net shape product and process development environment

Additive manufacturing made a revolution in the Manufacturing area by producing parts with less lead time and highest complexity. It creates parts in layer by layer manner using engineering design. Metallic components in all fields can be produced by Additive manufacturing because of its near net shape production and high quality production. Many Steels can be processed using Additive manufacturing methods. 17-4PH and 15-5 PH Stainless Steels are the precipitated hardened steels which exhibits better mechanical properties after Heat treatment. Even though so many Additive manufacturing Processes are there, Selective Laser Melting gives fully dense and quality parts. In this review paper, we have given an over view on the Microstructure, mechanical, corrosion properties and fatigue properties of 17-4 PH SS and 15-5 PH SS produced by SLM and comparison with conventional parts.KeywordsPrecipitation hardeningSolution annealingAging

The use of additive manufacturing (AM) in industrial applications is steadily increasing due to its near net shape production and high design-freedom. For metallic components, laser-based powder bed fusion (L-PBF) is currently one of the most widely used AM processes. During L-PBF, a component is manufactured layer by layer from a powdery raw material. The process is controlled by a multitude of parameters like the laser power, scanning speed and layer thickness, whose combination significantly influences the properties of the components. In this study, the influence of the L-PBF machine type and the influence of the powder batch are investigated by means of relative density, microhardness and microstructure of the components. For this purpose, three setups are defined, differing in the powder batch and machine type used. By comparing the process results of the additive manufacturing of different setups, the influence of the machine type and powder batch are determined. The considered material is stainless steel AISI 316L. The results revealed significant differences between all investigated properties of the additively manufactured components. Consequently, process parameter combinations cannot be transferred between different machine types and powder batches without verification of the component properties and, if necessary, special adaption of the process.

A finite-element analysis of magnetically driven recirculating flow in electromagnetic near net shape casting

Friction stir welding of additively manufactured Ti-6Al-4V: Microstructure and mechanical properties

Metal additive manufacturing technology of layer-wise stacking of 2 dimensional patterns is emerging in engineering components manufacturing. Nevertheless, limited materials selectivity is a critical hurdle for industrial adoption. Hard engineering components are good market penetration point because product design is limited by machining cost. Near net shaped product with complex design will be advantageous though net shape products cannot be manufactured by current state AM technology. In this context, applicability of a Fe base powder with multiple components for laser powder bed fusion AM was assessed. Powder layer was pre-placed on STS build platform and layer thickness was set to be 25 um. 2 dimensional patterns were overlaid according to continuous irradiation mode with outer contour formation. Laser input parameters were selected from pre-screening step with 5x5x3 mm3 model. After that, 10x10x10 mm3 samples were prepared with laser powder and laser scan rate changing. According to laser parameters, phase compositions and microstructures were reported. Optimum process window for the powder feedstock is reported. With respects to formation of defects such as distortion, interlayer debonding, cracking, and pores, solidification crack, non-uniformity of powder layer, and primitive bead characteristics were considered. In addition, effects of phase composition on corrosion behavior were investigated by anodic polarization.

Controlling the feature resolution and dimension of printed products using stereolithography requires a comprehensive understanding of compositional and printing variables. Balancing these variables adds more complexity to manufacturing near net shape products. In this study, the compositional variables examined include particle size and solid content using two resins, and printing variables include layer thickness and energy dose. Choosing the energy dose for curing depends on compositional variables and consequently affects the degree of scattering. The results shows that light scattering determines the changes in the feature resolution and lateral dimensions. The layer thickness only affects the feature resolution and not the lateral dimensions. The vertical dimension does not significantly change with the chosen variables. In this study, fine-tuning the variables is shown to produce parts with high precision and resolution. Both compositional and printing variables play a key role in achieving near net shape products.

In powder forming processes, the behaviour of powders during compaction, such as the mechanisms of density increase, density distribution, evolution of anisotropy, the shape of compacts in isostatic compaction, etc. significantly influence the quality of the products, dimensional and geometrical accuracy and material consumption. Further, the compacts that have been compacted at room temperature are subject to a sintering process; they undergo dimensional and geometrical change during the process; these are affected by the previous compaction process and density distribution. In recent years, the demand has been increasing for accuracy in the dimensions and shapes of products. Simulation of compaction behaviour of powders is, thus, of great importance for near net shape production. To simulate the behaviours of powders or granular materials, there are two approaches: one is to treat the powder based on continuum mechanics, and the other is to observe the movement of individual particles. In this article, we shall overview the state of the art regarding both types of simulation.

The technique of atomising liquid metal and compacting the spray to the deposit on a moving substrate combines advantages from cast, wrought and powder metallurgical materials. A production rate of several tons per hour requires precisely controlled processing. Parameters based on physical, metallurgical and technological knowledge have been determined by fundamental investigations in a special research program (SFB 372) of DFG (Deutsche Forschungsgemeinschaft). Because of the advantage of near net shape production as due to casting, this process avoids partially machining which leads to a reduction in production costs. Research on high carbon steel and cast alloys was done to study the applicability of this low cost spray cast technology instead of expensive powder metallurgy production.

The increasing demand for resource-efficient production methods is driving the development of new technologies. Sheet bulk metal forming (SBMF) offers the possibility to combine sheet metal and bulk forming operations. This allows the production of complex functional components with secondary forming elements from sheet metal. Compared to other production techniques such as machining, a more efficient use of material can be achieved. Further advantages are a near net shape production and increased strain hardening. SBMF processes are limited by forming technology boundaries. These include high forming forces, incomplete mould fillings and limited surface qualities. In this research, the possibility of enhancing the material flow, improving surface quality and reducing the tool loads in SBMF-processes is investigated by using a superimposed oscillation. The focus here is on achieving a high surface quality of components produced by forming technology and an enhanced material flow during forming. For this purpose, a forming process for ironing an axial gear geometry is superimposed with an oscillation in the main force flow.

Micro and mini manufacturing is becoming more important than before. Among micro and mini manufacturing processes, micro forming has economical and ecological benefits due to high production rate, low material scrap rate, net shape production, and improved mechanical properties through work hardening. Even though macro scale metal forming is well understood and has been extensively studied, these concepts cannot be applied directly to the micro scale metal forming [. In this paper, a conical mini-part was precisely evaluated from finite element (FE) simulation. The final geometry of the conical mini-part is affected by forming parameters of the deep drawing process (blankholder force, friction coefficient, speed of the deformation tools) and by the tool geometry. In order to reduce the geometry deviation, all the parameters must be studies separately to quantify their influence on the final mini-part geometry. This paper presents a study concerning the optimization of the forming process in order minimize the geometry deviation of the final parts. The main objective is to understand the factors that have the highest influence on the forming process of conical mini-parts and to modify them in such way that the resulted part is according to the designer specifications. The material used in this analysis is copper - zinc alloy with anisotropic properties. After the forming process of conical mini-parts is over and the part is removed from the forming tools, the geometry of the part is analysed and compared with the ideal shape. Due to cumulated effect of springback and other phenomena that affect the conical mini-part is not having the desired accuracy from the dimensional deviation point of view [2,. There are multiple factors that affect the mini-part geometry during forming process as: blankholder force, punch rounding radius, and side wall angle. The Dynaform 5.9.1 software was used to simulate the forming process. During optimisation process 27 simulations have been done. The part obtained after each simulation is analyzed and measured to quantify the deviation from the ideal part geometry. The presented optimization method is a good method to reduce the dimensional deviations. The advantages of this method are the reduced number of simulations tests that must be done and precision of the obtained results.

Characterization of biomedical Ti-16Nb-(0–4)Sn alloys produced by Powder Injection Molding

Mechanical, electrochemical and biocompatibility evaluation of AZ91D magnesium alloy as a biomaterial

Abrasive water jet (AWJ) can be effectively employed on a broad selection of work materials, ranging from polymers to lapideous materials and high grade steels. The AWJ cutting process involves several variables, including hydraulic, abrasive, mixing and cutting parameters. Moreover workpiece properties, mainly modulus and hardness, affect material removal type (cutting and deformation wear mode). This paper concentrates on the influence of the mechanical properties of the workpiece on kerf roughness that is achieving more and more attentions from manufacturers, aiming towards near net shape production. In particular, the same carbon steel (C40 UNI EN 10083-2) was used for all tests; two heat treatments were performed on different specimen sets. AWJ cuts on 'as is' (normalised) and hardened specimens (water-quenched) were realised using different traverse speed. The surface roughnesses of the kerfs at different depths were measured to evaluate process performance. A statistical analysis was carried out to assess the significance of the results. It was found that workpiece hardness affects surface finish in different ways, depending on water pressure, traverse rate and depth of measurement across the kerf. Such results support the theory about two different material removal mechanisms, activated at different levels of jet erosive power.

Due to their intermediate position between the machine and workpiece, tools represent the interface of the manufacturing system to the process. Near net shape production, new materials and techniques are the new challenges in metal forming and especially in tooling. A significant economical effect can be achieved through an increase in the life of tool elements, as well as through proper tool management strategies. The greatest problem connected with the preliminary estimation of tool life is the large scatter of service life for a series of identically designed tools. The uncertainty in estimating the expected service life of tools and thus the tooling costs per piece is caused by the enormous variety and confluence of damaging factors, the factory-specific character of tool life and the stochastic phenomenon of tool failures. From the confluence of aspects influencing tool life it is clear that there is no general recipe for increasing tool life and tool quality. Each of the influencing aspects contains some possibilities for increasing the service time of tools. This paper shows some examples of tool design and tool manufacturing and points out that a knowledge-based approach imitating the activity and knowledge acquisition of human experts can be the bridge between computer aided (CA) techniques and human experience in predicting expected tool life.