Despite the slowdown in the growth of Brazil’s economy in recent years, with the automotive industry in particular struggling, there is continuing optimism for the future of the country’s relatively young Powder Metallurgy community, both in academia and industry. This was the message from the 10th Latin American Conference on Powder Technology, PTECH 2015, which took place in Mangaratiba, some 120 km from Rio De Janiero, November 8-11, 2015.
The bi-annual PTECH conference celebrated 20 years of bringing together academics, PM production and industry suppliers to share their latest research and advances in PM production and applications. It also gave around 250 delegates from Latin America’s Powder Metallurgy and associated sectors the opportunity to network with a number of overseas participants and exhibitors representing powder, feedstock and equipment suppliers.
Dr Bodo Fink, Managing Director of GMC Feedstocks, and one of PTECH 2015 sponsors, told PIM International, “The PTECH conference is a fruitful platform to get in contact with metalworking industry and universities in Brazil. Face-to-face contact is essential in the MIM business, and Brazil shows a lot of new opportunities in the engineering, automotive, aerospace and medical sectors.”
Around 240 technical papers were presented at PTECH 2015, either in oral or poster sessions covering the following areas: Synthesis: Mechanical alloying, Metal Matrix Composites, Nanomaterials,
- Synthesis: Mechanical alloying, Metal Matrix Composites, Nanomaterials,
- Processing: PM compacting, MIM and Additive Manufacturing, Plasma Assisted Sintering and heat treatment
- Properties: Corrosion and mechanical properties,
- Applications: Wear resistant, biomaterials, magnetic materials.
Ana Cristina Marcucci and Dr Fink gave the plenary talk on feedstocks for high-tech ceramic and metal applications. Marcucci stated that MIM and CIM had not only become large scale and viable production processes over the past decade, but that in recent years PIM had also targeted other novel applications which required PIM feedstocks based on materials different from the well-established iron-nickel and stainless steels that are now commonplace.
They described the development of several CIM and MIM components in medical, automotive and machinery applications, giving details of materials processing and properties obtained. Various examples showing the benefits of PIM versus established shaping processes such as investment casting were shown.
MIM of rare earth alloys
L U Lopes and P A Wendhausen presented their research into the use of MIM for reactive metals such as rare earth based alloys. They stated that MIM is much less common as a manufacturing process in this area due to the challenges of preventing oxidation during the manufacturing process and contamination with binder residues. The authors reported on a literature review of the techniques developed to circumvent such issues, mostly focused on the fabrication of rare-earth based magnets, as well as the remaining technological challenges. These are mostly related to dimensional stability and anisotropic shrinkage that takes place in magnets with the presence of crystallographic texture.
Similarities between gelcasting and MIM
An interesting presentation on the gelcasting process was given by F S Ortega and L F Oliveira, who also compared the process with MIM. They describe the gelcasting process as a consolidation technique that consists of filling a mould with a highly loaded aqueous suspension followed by gelation due to the polymerisation of water-soluble monomers. Although this process has been widely used for shaping ceramic parts using colloidal suspensions, its application with metal powders is less well known due to rapid settling of larger and denser metallic particles. In their research HK-30 stainless steel powders with different grades (10F and 20F) were gelcast into cylindrical moulds (90 mm high) with the help of a suspending agent. The gelled bodies were dried, vacuum sintered and sliced across the settling direction in order to assess the effect of the suspending agent on particles settling. Both the sintered density and the microstructure were homogeneous along the cylinder axis, showing that any effect associated to particles settling could be avoided. Final density was close to the theoretical value, although the samples produced with 10F grade powder showed a small residual porosity. The microstructures were similar to those reported for this powder processed by MIM.
Self-lubricating steel composites
Tatiana Bendo and colleagues from the Universdade Federal de Santa Catarina presented a paper on self-lubricating composites containing second phase particles incorporated into the volume of the material. This appears to be a promising solution for controlling friction and wear in mechanical systems. The aim of this work was the development of steels with low friction coefficient through a precursor (SiC) that generates nanostructured carbon nodules in a ferrous matrix. The samples were processed by conventional PM route, namely single pressing using the fine powders also typically used in PIM, after granulating them. The purpose of producing granulates was to obtain a better distribution of the carbon nodules. The alloy composition studied was Fe-0.6C-3SiC using 2 wt.% of EVA as binder for the granulate. The influence of the fine sizes of iron and silicon carbide particles on the microstructure, mechanical and tribological properties were evaluated. The powders were homogenised in a “Y” type mixer, drum granulated, pressed and then plasma sintered in a single cycle combining binder extraction and sintering of the constituent components. The alloys have
achieved results close to alloys with same composition produced via PIM but with processing time and cost closer to that of conventional PM.
The PTECH 2015 conference proceedings will be in Materials Science Forum by Trans Tech Publications. The next conference in the series, PTECH 2017, will be held in Natal, Rio Grande do Norte, Brazil, in November 2017. Many thanks to Ana Cristina Marcucci for contributing material and images used in this review.