Papers by Keyword: Post-Processing

Abstract: This study investigates the fatigue performance of additively manufactured H13 hot work tool steel (AM-H13 TS) produced using the laser powder bed fusion (L-PBF) process with two distinct build orientations: vertical (V-BO) and diagonal with 45° (D-BO). A fixed volumetric energy density of 57.3 J/mm³ was employed for fabrication. The study compares the as-built AMH13 TS to its surface-finished counterpart, focusing on fatigue life and damage under fully reversed tension-compression loading conditions. The surface finishing processes involved electropolishing using commercial DLyte 100HF+ equipment, followed by mechanical surface refinement. The surface topography and roughness characteristics of the as-built and post-polished specimens were comprehensively analyzed using laser confocal scanning microscopy (LCSM). Scanning electron microscopy (SEM) was utilized to examine the microstructural features and fatigue mechanisms. The as-built AM-H13 TS exhibited high surface roughness due to the presence of satellites and partially melted particles, which are inherent to the L-PBF process. The surface-finishing approach substantially mitigated these surface imperfections, resulting in significantly improved surface quality and reduced roughness. As a result, the fatigue performance of surface-finished AM-H13 TS showed remarkable enhancement. The fatigue limit increased fivefold, from 100 MPa in the as-built condition to 500 MPa after surface finishing. SEM analysis revealed that the improved fatigue strength was primarily attributed to the reduction in surface roughness and the elimination of surface flaws, which acted as crack initiation sites in the as-built condition.

Abstract: Wire arc additive manufacturing (WAAM) has gained significant attention in recent years as a cost-effective and efficient method for fabricating complex geometries. This study investigates the effects of cold forging and annealing on mechanical properties of AISI 308LSi wall fabricated using an automatically controlled gas metal arc welding on a CNC machine. The multilayer WAAM wall manufactured at an optimized parameters was first machined to a fairly smooth surface. Thereafter, the wall samples were differently subjected to annealing at 930°C and cold forging processes to improve the mechanical properties. Microstructural characterization of the post-processed and as-deposited samples were performed using optical and scanning electron microscopy while the tensile and hardness properties were investigated using Instron universal testing machine and Vickers hardness tester respectively. Annealing process was found to improve the tensile properties while the cold forging improved hardness of the deposited WAAM wall. These findings offer valuable insights into optimizing post-processing techniques for WAAM parts, especially 308LSi stainless steel and contribute to the advancement of this technology for industrial applications.

Abstract: There is significant interest today in additive manufacturing which is automatically producing 3D objects by adding layer-upon-layer of material. Additive manufacturing offers a revolutionary way of creating parts despite their geometric complexity compared to conventional manufacturing methods. Today, both the number of additive manufacturing processes and the materials available has developed rapidly which leads to the easy integration of topology optimization with it to improve structural performance in engineering fields such as in an automobile, aerospace, medical and biomechanical industries. The principal aim of this paper is to study the post-machining process of topology optimized parts. Topology optimization is an intelligent approach to get the best reduce weight design and achieve optimal performance at the same time in many fields. Yet unfortunately, it still faces some post-machining issues.

Abstract: This paper introduces novel TCAD post-processing techniques for SiC MOSFETs with the aim of understanding which parts of the device limit the on-state performance. Typically, analytical models of MOSFETs are used as a starting point for the TCAD design process or as a simple way to understand the influence of complex design choices, as discussed in the works of [1-3]. These lumped element models result in a relatively straightforward approach because they explicitly identify the contributions of the regions of the transistor, facilitating the understanding of basic design choices and performance trade-offs. However, the simplifications introduced in analytical models limit their applicability to advanced device structures such as aggressively scaled transistors or trench MOSFETs with cellular layout. This paper presents mathematical techniques based on post-processing of TCAD simulations that combine the accuracy of numerical Finite Element studies with the interpretability of lumped element analytical models.

Abstract: The most important parameter, characterizing the rheological properties of steels and alloys, is the strain resistance. The new method of testing cylindrical specimens for torsion with variable grip’s accelerations is proposed (application No. 2018132149 of 07.09.2018 for the patent of the Russian Federation for the invention). This method is designed to study the rheological properties of steels and alloys mainly in a hot state. However, this method is universal and can be used to determine strain resistance of materials in a cold state. The article is devoted to the applicability evaluation of the proposed torsion testing method, to study the rheological properties of materials in a cold state. It’s done on the basis of comparison of the hardening curves, obtained during the testing of specimens for tensile and torsion. The CrWMn steel was used. The results show that the hardening curves obtained during the torsion and tensile tests are close, and the yield stress values differ by about 3%. It can be assumed that the developed method of torsion testing allows to obtain reliable values of the material’s strain resistance in a cold state.

Abstract: Laser metal deposition (LMD) is an additive manufacturing process highly adaptable to medium to large sized components with bulky structures as well as thin walls. Low surface quality of as-deposited LMD manufactured components with average roughness values (R_a) around 15-20μm is one of the main drawbacks that prevent the use of the part without the implementation of costly and time-consuming post-processes. In this work laser re-melting is applied right after LMD process with the use of the same equipment used for the deposition to treat AISI 316L thin walled parts. The surface quality improvement is assessed through the measurement of both areal surface roughness S_a(0.8mm) QUOTE and waviness W_a QUOTE (0.8mm) parameters. Moreover, roughness power spectrum is used to point out the presence of principal periodical components both in the as-deposited and in the re-melted surfaces. Then, the transfer function is calculated to better understand the effects of laser re-melting on the topography evolution, measuring the changes of individual components contributing to the surface roughness such as the layering technique and the presence of sintered particles. Experiments showed that while low energy density inputs are not capable to properly modify the additive surface topography, excessive energy inputs impose a strong periodical component with wavelength equal to the laser scan spacing and directionality determined by the used strategy. When a proper amount of energy density input is used, laser re-melting is capable to generate smooth isotropic topographies without visible periodical surface structures.

Abstract: Metal 3D AM (Additive Manufacturing) has been becoming a more common production method for larger variety of parts. In this review the current situation and future development trends of the 3D metal AM are presented, concentrating on the SLM (Selective Laser Melting) technology. A holistic approach to the AM as a digital manufacturing method is presented and different manufacturing aspects of the AM production are identified. The most promising aspects for the future development are the automatization of the AM design tasks and automatization of the production. With the development of these aspects the production and cost efficiency of the metal AM can be increased to a more competitive level compared with other manufacturing methods.

Abstract: In order to solve the problem of openness, intelligence and low integration in the current machining robot control system, STEP-NC standard is introduced into the field of robot machining, and defines the STEP-NC data model of industrial robots. The 6R industrial robots are used to build the machining platform and the connection between the machining robot and the CAD / CAM system and the integrated data stream structure are discussed. The key issues involved in the post processing of the machining robot are studied. Taking the 6R robot as an example, the robot prototype system is established, and the kinematics solution in the post-processing process is studied and deduced. The cutting and post-processing system platform of cutting robot was established and the sample art machining was completed. The experimental and simulation results show that the system can complete the machining process of the cutting robot and generate executable robot machining instructions.

Abstract: Usually, generating parts with complex surfaces, especially three-dimensional (3D) curved-surface blades, involves difficult designing, complicated manufacturing processes, and low production efficiency. In this study, by integrating 3D curved-surface modeling and the rapid prototyping functions of the pro/E software platform with computer-aided design, layered manufacturing, and material curing technologies, an improved process was realized. The once-challenging fabrication of irregular curved-surface blades was transformed into a simple technique of making planes. By selectively curing the raw material, as demonstrated in this study, complex surfaces can be manufactured rapidly, thus shortening research and development stages of new products, reducing costs, and endowing manufacturers with an improved capacity to research and develop products with greater competence and accuracy .

Abstract: Ohmic contacts with low contact resistance, smooth surface morphology, and a well-defined edge profile are essential to ensure optimal device performance. Ohmic contacts often require annealing under vacuum at over 1000 °C, whilst high-κ dielectrics are usually annealed in O₂ rich ambient at temperatures of 800 °C or less, affecting the specific contact resistivity (ρ_C) and RMS surface roughness. Therefore, protection of the Ohmic contacts during the annealing of a high-κ dielectric layer is a key enabling step in the realisation of high performance MOSFET structures. In order to prevent damage during the high-κ formation, a passivation layer capable of protecting the contacts during annealing is required. In this work we have investigated the suitability of PECVD silicon nitride as a passivation layer to protect Ohmic contacts during high temperature, oxygen rich annealing.