Pan American Materials Congress: Advanced Manufacturing: Materials Processing
Sponsored by: Third Pan American Materials Congress Organizing Committee
Program Organizers: Sonia Brühl, UTN - National University of Technology; Ricardo Castro, University of California, Davis; Dachamir Hotza, UFSC

Tuesday 10:20 AM
February 28, 2017
Room: Marina D
Location: Marriott Marquis Hotel

Session Chair: Ricardo Castro, University of California, Davis; Sonia Brühl, UTN

10:20 AM  Invited
Carbon Based Coatings Deposited on Nitrided Stainless Steel: Study of Thermal Degradation: Sonia Brühl1; Eugenia Dalibon Bähler1; Vladimir Trava-Airoldi2; Naureen Ghafoor3; Lina Rogström3; Magnus Oden3; 1National University of Technology; 2Instituto Nacional de Pesquisas Espaciįis (INPE); 3Linköping University
     Amorphous hydrogenated carbon (DLC) coatings have a high hardness dependent in the relative amount of sp3/sp2 bondings. They exhibit also an extremely low friction coefficient and are chemically inert. But some applications are limited because adhesion is poor over soft substrates and it is also not stable at high temperatures, degrading into graphite and loosing hardness. In this work DLC coatings were deposited on precipitation hardening stainless steel (PH Corrax) which was plasma nitrided before the coating deposition. The samples were submitted to annealing treatments of an hour duration at different temperatures from 200 C to 600 C, together with a control group, only coated but not nitrided. After each annealing cycle, Raman Spectroscopy, nanoindentation and microscopy were used to check film properties.It was demonstrated that the nitriding pre treatment improved not only adhesion but also the thermal stability of the DLC, slowing degradation and preventing delamination.

10:50 AM  
Conceptual-Functional Model of Drilling Electrochemical Discharge Machining: Gerardo Hernandez1; Alejandra Hernandez1; 1COMIMSA
    Today the advanced materials that are used in industries like aeronautic, automotive, mold and die industries, has triggered the application of advanced machining processes to fulfill the requirements for material forming, dimensional accurate, and surface finish for machining of hardened and brittle materials. Among advanced machining processes for facing these challenges is being explored the application of the electrochemical discharge machining. This machining process has a complex dynamic behavior, the electrodischarge phase erodes the workpiece through thermal mechanism, whilst electrochemical phase dissolves the workpiece through the current density, Faraday’s laws. This paper highlights the process of energy transformation through the power supply, tool, electrolyte and workpiece by means of a conceptual/functional model. Holes were made in a workpiece of high strength low alloy steel, a brass tool, and sodium chloride dissolved in deionized water like electrolyte. Respective microstrure analysis and measure of material removal rate and surface roughness were developed.

11:10 AM  
Deep Drilling in Soda-lime Glass Using Air Jet Assisted Electrochemical Discharge Machining (ECDM): Rajendra Arya1; Akshay Dvivedi1; Pradeep Kumar1; 1Indian Institute of Technology, Roorkee
    ECDM is a preferred machining process for non-conductive materials like glass, ceramic etc. in micro-domain. In ECDM, the material is removed by thermal and chemical action. Micro hole of depth more than 1000 µm has not been reported. Poor electrolyte replenishment in a machining gap between tool and workpiece is one of the main reason behind it. In this experimental investigation a new approach has been used to enhance electrolyte replenishment. In which an air jet has been assisted to ECDM. The air has been supplied in pulse mode with 1second on time and 1 second off time. Apart from replenishment, the air jet also removes debris from machining zone. The maximum depth of 2500 µm was achieved by air jet assisted ECDM.

11:30 AM  
Mechanisms and Influence of In-situ Pre-heating during Friction Welding: Daniel Adams1; Jerry Gould2; Michael Skinner1; Tom Budd1; 1Manufacturing Technology, Inc. (MTI); 2EWI
    Friction welding processes create heat for joining through high speed relative contact of the opposing workpieces. The mechanism for such heating is known to transition from sliding friction to one based on continual plastic deformation. The transition between these heating regimes is characterized by a short duration spike in the shear loads necessary to maintain the desired relative motion. These instantaneous high shear loads govern designs for current welding systems. This work investigates the use of in-situ heating for mitigating such shear loads. A hybrid system has been developed that incorporates elements of both resistance based upset welding (UW) as well as linear friction welding. Studies have been conducted to define relationships between processing conditions and resulting shear load variations for some representative material systems (steels, Al-alloys). Work is supported by metallographic interpretation, as well as baseline mechanical properties assessments.

11:50 AM  Invited
Microstructure-processing-property Relationships in Nanocrystalline Ceramics Produced Using Current-activated, Pressure-assisted Densification (CAPAD): Javier Garay1; 1University of California San Diego
    The benefits of using electric currents and mechanical pressure for densifying powders have been realized for decades. Recently, there has been a worldwide resurgence of activity and interest in current-activated, pressure-assisted densification (CAPAD) driven primarily by two distinct factors: the efficiency of the process and the unique materials that can be fabricated by it. First, with the aid of high electric currents, it is possible by using CAPAD to consolidate powders to full density much faster and at lower temperatures than by traditional methods such as pressureless sintering and hot pressing (HP). The second and perhaps more tantalizing motivating factor is that the benefits go beyond efficiency and offer a platform for producing materials that are extremely difficult, if not impossible, to produce by other methods. We will present results on recent work on producing dense, large-sized, nanocrystalline materials for optical and magnetic applications.

12:10 PM  Invited
Sintering of Anisotropic Porous Microstructures: Eugene Olevsky1; Andrey Maximenko1; Diletta Giuntini1; Rajendra Bordia2; 1San Diego State University; 2Clemson University
    High performance electrochemical systems (e.g. electrodes for solid oxide fuel cells, gas separation membranes and batteries) have microstructural requirements that require using graded, hierarchical and/or anisotropic porous materials. A multi-scale modelling framework for sintering analyses is utilized for the description of the experimentally observed evolution of the pore orientation in textured porous structures. The meso-scale level of the sintering simulations assumes a bi-porous material structure in accord with the characteristics of the materials utilized in the experiments. The evolutions of both the meso-scale domains and the macroscopic volume of the analyzed porous material are modelled by the finite-element method. The presentation describes the differences between the small and large pore evolution based on the specifics of viscous and diffusional mass transport during sintering processes.

12:30 PM  
Finite Element Modelling of Current-activated, Pressure-assisted Densification (CAPAD): The Role of Materials Properties and Geometry on Thermal Gradients: Meir Shachar1; Alexander Dupuy2; Yasuhiro Kodera2; Javier Garay1; 1University of California, San Diego; 2University of California, Riverside
    Current-activated, pressure-assisted densification (CAPAD) is a densification process that uses electrical currents to heat the sample and its holder under elevated pressures. Also known as spark plasma sintering, CAPAD is renowned for being able to deliver high heating rates (up to 600°C/min) to its samples, reducing conventional processing times from hours to minutes. To better understand the CAPAD system and to investigate the impacts of design choices on operating conditions, a finite element model of CAPAD was constructed via COMSOL. The model has the capability to compute mechanical, thermal, and electrical variables at all points of space and time. Steady state and transient state studies were conducted for sweeps of sample material parameters (thermal conductivity, electrical conductivity, and heat capacity) and system geometry. Analysis of temperature gradients within samples are performed as a function of these sweeps. Key insights for the control of temperature gradients are discussed.