The EPMA Keynote Papers for Euro PM2017 are:
Role of Beta-stabilizer Elements in Microstructure and Mechanical Properties Evolution of PM Modified Ti Surfaces Designed for Biomedical Applications
Dipl.-Ing Julia Ureña
University Carlos III Of Madrid, Spain
The aim of this work focuses on the evaluation of modified Ti surfaces produced by powder metallurgy. These new designed materials are processed by deposition and diffusion of a stable aqueous suspension prepared in one case from micro-sized Nb powder (Ti ß-stabilizer element); and in another case, from Nb plus the addition of ammonium chloride, NH4Cl, (thermo-reactive diffusion process). Different design parameters such as: diffuser element (Nb or Mo), state of the Ti substrate (green or sintered) and the treatment process (diffusion or thermo-reactive diffusion) lead to all the surface-modified materials, GreenTi-Nb, SintTi-Nb and Ti-NbNH4Cl, GreenTi-Mo, SintTi-Mo and Ti-MoNH4Cl. They present a gradient in composition and microstructure (ß – a/ß – a phases) resulting in an improvement in some of their mechanical properties: (1) higher micro-hardness in all the modified materials, and (2) lower elastic modulus (more similar to that of the human bone) in those without NH4Cl.
Sintering Iron And Steel: Are There Indications For Defect-Activated Sintering?
Dr Torsten E M Staab
Fraunhofer ISC Wuerzburg, Germany
Defects in powder metallurgical samples may enhance diffusion processes during sintering. Samples of high purity nickel reduction powder and pure carbonyl iron are prepared by interrupted sintering, i.e. removing the furnace at the target temperature and rapidly cooling the samples, which are then investigated by analytical methods like positron annihilation lifetime spectroscopy (PALS). Thus, we can follow the sintering process by changes in the microstructure. These results are compared to heavily deformed reference samples (iron taken from literature) to determine the recovery temperature (0.4 of the melting temperature), i.e. annealing of dislocations. We estimate an effective powder particle size, which can be used to model the shrinkage by a modified two-particle model. The results for the two systems will be compared. For larger samples (10-30mm in diameter) we follow the shrinkage by thermo-optical measurements to determine influences of the pressing tools by monitoring the shrinkage at different height positions during one run.
Implementation of Advanced Characterization Techniques for Assessment of Grinding Effects on the Surface Integrity of WC-Co Cemented Carbides
Prof Dr Luis Llanes
Universitat Politecnica Catalunya, Spain
Grinding is a key step on the manufacturing process of WC-Co cemented carbides (hardmetals). A systematic study of grinding effects on the surface integrity of hardmetals is conducted. It is done by combining diverse advanced characterization techniques: XRD, FESEM/EBSD, FIB – 3D tomography and TEM/PED. The study is conducted in a fine-grained WC-Co grade with three different surface finish conditions: ground, polished, and ground-termal-annealed. It is found that grinding induces significant alterations in the surface integrity of hardmetals. Main changes included generation of a topographic texture, anisotropic distribution of microcracks at the subsurface, phase transformation of binder, and large compressive residual stresses. On the other hand, high temperature annealing resulted in: relief of residual stresses, but without inducing any change in terms of damage within the carbides; as well as reversion of phase transformation and emergence of an unexpected microporosity within the binder.
Can Industrial Standards Disregard Thermodynamics And Material Science?
Dr Gian Filippo Bocchini
PM Consultant, Italy
At the beginning, the apparently strange, or absurd, question is explained. Two cases are discussed. The DIN Standard 30910-4: Sintered metal materials. ,,, Part 4 …, ignores the effects of carbon content on steel’s properties and microstructure. The Standards ASTM B935 – 16, Standard Guide for Steam Treatment of Ferrous (PM) Materials, and MPIF 35 2016, Material Standards for PM Structural Parts, in the section Engineering Information, neglect the Fe-O phase diagram and the stability of iron oxides as the temperature varies. The questionable points and the inconsistencies of the Standards are analysed. Then, we advance hypotheses about any possible reason why certainly competent people “forget” materials science and thermodynamics. No certainty as to the most likely hypotheses, but it seems sure that Standards susceptible to strong criticism do not contribute to promote P/M applications. In the interests of P/M technology, its image and its development, effective corrective actions are proposed.
EPMA Keynote Paper Awards winners for Euro PM2017
Left to right: Dr Gian Filippo Bocchini (PM Consultant, Italy), Dipl.-Ing Julia Ureña (University Carlos III Of Madrid, Spain), Dr Torsten E M Staab (Fraunhofer ISC Wuerzburg, Germany), Dr Jose Manuel Torralba accepting the award on behalf of Prof Dr Luis Llanes (Universitat Politecnica Catalunya, Spain) and Philippe Gundermann (EPMA President)
© Andrew McLeish Euro PM2017