Cristina Ileana Pascu

Bulk titanium for structural and biomedical applications obtaining by spark plasma sintering (SPS) from titanium hydride powder

Titanium is a low density element with excellent mechanical properties, and is an attractive material for structural and biomedical applications. In recent years, a new process technology is emerging by which titanium and titanium alloys can be obtained by using titanium hydride (TiH2) as a precursor for Ti and its mixture with alloying elements. The feasibility of this manufacturing approach has been fully demonstrated from powder to sintering and from microstructure to mechanical properties. In this paper, a study concerning powder metallurgy processing of Ti by spark plasma sintering (SPS) route is presented. The influence of the technological parameters on the hardness and microstructures change during SPS has been studied. The experimental results are related to microscopic, thermal, and mechanical analysis.

Study about the Influence of Two-Steps Sintering (TTS) Route for an Alloy Based on Titanium

This paper describes the influence of two-steps sintering regime temperatures concerning the final properties of titanium hydride based alloy obtaining by Two-Steps Sintering (TTS) route, which is a method that is part of the Powder Metallurgy (PM) technology. The initial titanium hydride powder has been mixed with some metallic powders as: Alumix, Mn, Zr, Sn and graphite was added in different proportions for improving the final mechanical properties. The Two-Steps Sintering (TTS) route have been applied for obtaining a low-cost Ti- alloy. The effect of the sintering regime temperatures on the height and diameter shrinkages and density for these alloys based on titanium hydride powder was studied

Implementation of Total Productive Maintenance Principles for Quality Improvement in an Automotive Company

In the automotive field, the application of Lean Manufacturing principles has become a common practice in recent decades. One of the basic methodologies of Lean philosophy is the Total Productive Maintenance (TPM). The TPM includes a number of methods initially designed to ensure the continuous operation of the machines involved in the production process so that production is never interrupted. In this paper some of the most important steps in quality improvement by implementation of TPM in an automotive company are presented. It is described the monthly implementation extent of TPM indicators starting from 2014 until now, especially on the production lines of the factory. Finally, the major benefits of TPM principles implementation in the company are highlighted.

Aspects about the Quality Control at First Article Inspection (FAI) for Parts Obtained by Materials Composites Used in the Railway Sector

In the railway sector, on the prototyping phase of product made by composite materials, it is necessary the implementation of a strict quality control using the instrument First Article Inspection (FAI). In this paper some of the most important steps in quality control implementation of FAI for composite parts at the prototyping parts made of composite materials in the railway field are presented. Thus, the necessary steps for developing FAI and the process diagram are given. Also, the method FMEA process is presented in order to eliminate the risks of errors and defects during the development of the technological process for obtaining the composite piece.

Research about the Quality of Bulk Titanium Materials Obtained by Powder Metallurgy Technology from Titanium Hydride Powder Used for Automotive Components

Titanium has excellent mechanical properties, low density, high chemical stability, good heat transfer properties and a good corrosion resistance. In recent years, a new process technology is emerging by which titanium and titanium alloys can be made by sintering titanium hydride (TiH2) and its mixture with alloying elements. The feasibility of this manufacturing approach has been fully demonstrated from powder to sintering and from microstructure to mechanical properties. This paper describes a study concerning Powder Metallurgy (PM) technology processing of Ti by conventional PM and non-conventional PM method such as Spark Plasma Sintering (SPS) route. The influence of the technological parameters on the micro-hardness and SEM microstructures during bulk titanium materials processing has been studied. The STATISTICA program has been used to monitor the influence of the technological parameters on the micro-hardness of bulk titanium processed products. The tribological behaviour of the bulk titanium materials on the basis of the coefficient of friction and wear rate is presented, too.

Aspects about Implementation of Lean Manufacturing Principles for Quality Improvement in a Production System for Automotive Industry

Now, worldwide, the Lean Manufacturing system represents the most comprehensive management philosophy within a manufacturing process. One of the basic principles of Lean Manufacturing is 5S process which involves the risks and wastes eliminating and it is considered a key of worker and equipment’s safety. Therefore, during the last years, 5S was expanded to 6S by the Safety adding. Thus, in this paper aspects about 6S process implementation on a manufacturing company of automotive components is presented. The monthly implementation extent of each 6S process indicators from 2013 until now is described, especially on the production lines of the factory. Finally, the major benefits of the introduction of the 6S principles in the company are highlighted.

Aspects about Sintering Behaviour of a Titanium Hydride Powder Based Alloy Used for Automotive Components

For this study with high originality, some aspects about the sintering behaviour of Titanium based alloy used for automotive components are presented. This paper presents the experimental results concerning the processing of Ti based alloy by Powder Metallurgy (PM) technology. The initial powder mixture consists in TiH2 micrometric powder particles that have been combined with some metallic powders for improving the final mechanic-chemicals and functional properties for using in the automotive industry. The classical PM route have been applied for obtaining a low-cost Ti- alloy.As a result it was compulsory to study the parameters that influence the densification process and the sintered properties, depending on the sintering temperature. The experimental test results were processed using the STATISTICA program. Therefore the influence of these sintering temperatures on the height and diameter shrinkages, density and hardness for the alloys based on Ti micrometric powders has been studied.

Research about Surface Quality of Polytetrafluoroethylene (Teflon) after Inner Turning

For this study with high originality, a teflon bushing with outer diameter of 58 mm and 32 mm internal diameter has been turned. After inner turning with various cutting feeds, the part has been cut in half to measure roughness. The roughness parameters Ra, Rz and Rq have beeen measured with an electronic roughness tester Mitutoyo, Japan, SJ-201 P. The micro-asperity images for each of the 6 samples performed are presented in the paper. Diagrams with the variations of roughness parameters are also given in this study. The trend is the increasing of roughness values with feed increasing, but some abnormalities also appear in samples 3 and 4 for Ra and Rz. At sample 5 for Rz parameter and sample 6 for Rq parameter a decreasing of values occurs, although geometrically there should be with ascending tendencies. It follows that in teflon turning the cutting process is not uniform, although there are no marks on the blade. However, because this material is not metallic, it does not have a uniform structure, which influences the resulted roughness. This is the cause of the anomalies established by these experiments.

RESEARCH ABOUT 18CrNi5 STEEL MACHINABILITY BY CUTTING

There have been made experiments on 18CrNi5 steel by external cylindrical turning, collecting the resulted chips. In this paper the shapes and sizes of the resulted chips, explaining their correlation with channel dimensions on the front face of cutting tool, according to and chip deformation sections are analyzed. Also, the forms of resulted chips in relation with parameters of cutting process are explained. Keywords— chips forms, chip section, 18CrNi15 steel, turning.

Research on the Manufacture of some Tungsten-Copper Composite after Vacuum Sintering

The paper presents the results of the experimental research carried out in order to obtain pseudoalloys WNiCu used in electrical industry, for the electrical apparatus of high tension and great power. As a result it was compulsory to study the parameters that influence the densification process and the sintered properties, depending on the grain-size distribution of tungsten powder, compaction pressure and sintering temperature in vacuum. Therefore, it has been studied the influence of these parameters on the density, hardness and microstructures changes for the composites with 78%W-2%Ni-20%Cu, (% wt). The better results were obtained for the value of 1350 0C for the copper infiltration temperature.