Advanced Materials Research Vols. 83-86

Abstract: Plasma spray processes have been widely used to produce high performance coatings of a wide range of Materials (metallic, non-metallic, ceramics), offering protection from, eg. wear, extreme temperature, chemical attack and environmental corrosion. To obtain good quality coatings, spray parameters must be carefully selected. Due to the large variety in process parameters, it is difficult to optimize the process for each specific coating and substrate combinations. Furthermore modelling the spray process allows a better understanding of the process sequences during thermal spraying. Good agreement of the virtual spraying process with the real coating formation is achieved by modelling the particular process steps. The simulation of coating formation to estimate the process parameters is an important tool to develop new coating structures with defined properties. In this work, the process of plasma sprayed coating has been analyzed by numerical simulation. Commercial code is used to predict the plasma jet characteristics, plasma –particle interaction, and coating formation. Using this model we can obtain coating microstructure and characteristics which form a foundation for further improvement of an advanced ceramic coating build up model.

Abstract: Continuous composition gradients of several millimetres were generated in commercial WC-Co cutters to improve their shock resistance. This important gradation was obtained in one-step by using the imbibition process. The effects of this thermal processing were analysed in terms of microhardness, cobalt concentration and WC grain size. A gradient of a 300 HV amplitude is measured in the 8 mm-height sample treated by the imbibition process in association with a boron-rich coating. This gradient was preserved after the HPHT (high pressure – high temperature) step used for the diamond table deposition on the WC-Co cutter. To our knowledge, such gradients have never before been reported and should certainly increase cutter service life.

Abstract: The presented article proposes a laser based polishing operation which consists in the application of a laser beam in a very controlled way. The work presents several polishing tests carried out with CO2 and High Power Diode Lasers, for a DIN 1.2379 tool steel tempered up to 62HRC. This material is commonly used for injection moulds and inserts for stamping dies. The Laser Polishing tests results have been used as the input data for a design of experiments (DoE), therefore the optimum operation parameters for the process as well as its degree of influence in the melted surface have been defined. Experimental tests have been performed from different initial roughness values obtained by High Speed Milling operations. Reductions of final roughness higher than 80% have been obtained with respect to the initial roughness, with values below 0.8μm Ra.

Abstract: The decrease of the bearing length in the aluminum extrusion processes results in an increase of the material flow and offers, through this, the possibility for correction and optimization. This study presents a simulation-based optimization technique which uses this effect for optimizing the material flow in a direct multi-hole extrusion process. First the extrusion process was numerically calculated to simulate the production of three rectangular profiles with equal cross sections. Here, the die orifices were arranged at various distances to the die centre, which lead to different profile exit speeds. Based on the initial numerical calculation, an automated optimization of the bearing length with the adaptive-response-surface-method was set up to achieve uniform exit speeds for all profiles. Finally, an experimental verification carried out to show the influence of the optimized die design.

Abstract: Any useful object is commonly made from selected engineering materials with proper shape and dimension. The selection of materials and manufacturing processes is an important criterion towards the production of useable and affordable objects. The technologies behind this knowledge are needed to acquire through study, proper education, practical training and scientific research related to Materials and Manufacturing Engineering (MME). Allah (swt), the sources of all power and knowledge, has bestowed the Guide Book, the Holy Qur’an through His beloved Messenger Prophet Mohammad (pbuh) to the mankind. Allah (swt) narrated various stories in many Surahs of the noble Qur’an related to applied science and technology. This paper is an attempt to view the integration between the revealed knowledge and the science and technology based knowledge related to engineering materials and manufacturing processes. Finally, stresses have been given to acquire knowledge on science and technology based education and understanding, and disseminate it for the cause of humanity.

Abstract: Direct Laser Metal Deposition (DLMD) is an emerging technique in the group of Material Accretion Manufacturing (MAM) processes because of the possibility to fabricate and to repair a wide range of metal components with a complex geometry, starting from metal powders. DLMD is a technology which combines computer aided design, laser cladding and rapid prototyping. Fully dense metallic parts can be directly obtained through melting coaxially fed powders with a laser. The success of this technology in the die and tool industry depends on the parts quality to be achieved. An accurate control of the parameters such as laser power, spot diameter, scanning speed and powder mass flow rate is fundamental to obtain the required geometric dimensions and material properties. In this work, the performance of the DLMD process was examined in terms of hardness, porosity, microstructure, and composition. A fitting equipment was built and used for the experiments together with a CO2 laser machine with a maximum power of 3 kW. The material used for experimental tests was Colmonoy 227-F, a Nickel alloy specially designed for glass container mould protection and restoration.

Abstract: Selective Laser Sintering (SLS), has become one of the most popular technique in the layer manufacturing processes because of the ability to build complex geometries models with a wide range of materials. Recently, the interest in SLS is mainly focused into metals because of the possibility of producing models not only for the prototyping step but also as functional parts. Driven by the need to process nearly full dense objects, with mechanical properties comparable to those of bulk materials and by the desire to avoid long post processing cycles, Selective Laser Melting (SLM) has been developed. SLM represents an evolution of the SLS process: in the first one the complete melting of powder occurs rather than sintering or partial melting of the second one. SLM, is mainly suitable to produce tools and inserts with internal undercuts and channels for conformal cooling for injection molding. A careful control of the parameters which influence the melting and the amount of energy density involved in the process is necessary to get parts with optimized quality. The aim of this paper was to study the effect of the main process parameters (laser power, scan speed, scan spacing, hatch spacing, scanning strategy) and of thermal treatments on the quality of built parts in terms of hardness, density, microstructure, and mechanical properties. The 18 Ni Marage 300 steel, one of the most used materials in the die industry was investigated, using a Nd:YAG laser with a maximum power of 100W.

Abstract: Laser processing of sheet metals (such as cutting or welding) involves heating of the substrate material by laser beam with temperature in the substrate materials reaching the melting temperature. Therefore, such laser processes consist of heating, melting and solidification of the substrate metal. An important topic in laser processing simulation is the modeling of the heat source (distribution of heat input). The interaction of laser beam with a molten metal pool is a complex physical phenomenon that still cannot be modeled rigorously. Laser beam as a heat source causes highly non-linear temperature distribution across the cut or weld and various heat source modeling approaches have been reported in the literature. In general, the distribution of heat input can be classified as superficial and volumetric. In this paper, a moving volumetric heat source model is presented. Using the proposed heat source model, laser cutting process is simulated and residual stresses generated in the cutting region are predicted.

Abstract: Apart from other factors such as die design and manufacturing, heat treatment, working conditions etc, performance of hot extrusion die can directly be related to the billet quality used in the extrusion press. The purpose of this paper is to investigate the effect of Al-6063 billet source (primary or secondary) on extrusion die life based on microstructural and statistical analyses. In microstructural investigation, secondary (remelt) billet cast in-house at local extrusion plant is compared with primary (smelter) billet by applying different material characterization techniques including optical microscopy, hardness measurement, X-ray diffraction (XRD) analysis, and energy dispersive spectroscopy (EDS). The statistical study is based on the failure history of some 53 hollow-profile dies in which the effect of billet quality on various measurable process parameters including extrusion ratio, billet temperature, exit temperature and repeated nitriding is analysed and related with useful die service life. Comparatively coarse grain structure, non-homogeneous distribution of secondary phases, and high hardness in the case of secondary billet were found responsible for poor die performance as observed in statistical investigation of failed dies. Two types of regression models are also proposed for prediction of die life in terms of secondary billets’ usage and measurable influencing parameters. Using current results, some suggestions during in-house billet preparation of secondary billets have been devised for improved die life.

Abstract: Clay has been used in Jordan as a building material for decades. This paper investigates the effects of adding olive husk –another locally available solid waste material- on the mechanical properties of the clay composite, and its modification of the ductility and thermal resistance for use as an insulating material. Laminated Metal Tooling (LMT) process will be used to manufacture the dies required to cast and dry the test specimens. A discussion will also be included regarding the eligibility of the material for the use as a low-cost, high efficiency insulating material depending on the manufacturability of husk-enhanced clay sheets.