Metal Powder Industries Federation Research Articles

Machining pre-sintered compacts of a sinter-hardenable powder metallurgy steel: A novel methodology for selecting sintering temperatures for the optimum machinability

Machining of compacts sintered at a temperature below the final sintering temperature, i.e., pre-sintered compacts, is a promising avenue that deals with the issues in machining sinter-hardened compacts of a powder metallurgy (PM) steel, as well as their green counterparts, i.e., green machining. The present study analyses this avenue by performing a turning operation on the compacts prepared from a Rio-Tinto-produced FLC-4608 (Metal Powder Industries Federation denomination, standard 35) sinter-hardenable steel powder-premix pressed to nearly 7.00 g/cm3 density sintered at 600 °C, 800 °C, 1000 °C, and 1150 °C (the temperature in the conventional sinter-hardening cycle), using a cutting tool comprised of Seco-make DCGW 07 02 04 – AL insert and SDNCN 12 12 M 07 holder. It was found that at a fixed cutting velocity and feed rate, an increase in the sintering temperature affects the machinability as follows: on one hand, it increases Fc (cutting force component in the direction of cutting motion) and enhances difficulties in chip formation and handling; but on the other, it improves the surface finish of the machined surface and reduces the size of exit-edge-breakout (damage at the edge from where the cutting tool leaves the workpiece during machining). Given these opposing trends, a novel methodology was proposed to identify the range of appropriate sintering temperatures that enables the optimum machinability of pre-sintered compacts over both green machining and the machining of sinter-hardened counterparts. In this methodology, a newly defined machinability criterion, the ratio of machining outcome to machining effort, was graphically represented with the machining effort. Its significance in design for manufacturing (DFM) could be referred to from the current report. Nevertheless, based on the methodology, the 750 °C to 850 °C was identified as the range of appropriate sintering temperatures for the subject material-tool pair. Overall, this study is potentially helpful to the domain industries for improving the manufacturing process flow with due consideration of machining pre-sintered compacts.

State of the PM industry in North America 2023

Rodney Brennen, president of the Metal Powder Industries Federation (MPIF) discusses recent trends in the North American powder metal industry, and what challenges and opportunities lie in store.

Evaluation of hardness and density properties of sintered Inconel 718 using palm oil-based binder

This paper investigates the effect of palm oil-based binder on hardness and density of sintered Inconel718. Palm stearin (PS) is the palm oil derivative, which has been formulated and evaluated as possible alternative binder system. The variety of PS contents can be an advantage during debinding process as it can be removed gradually to maintain the shape of the debound part. At different heating temperatures, each binder contents melts, leaving different impurities. The remaining impurities help to form capillary holes for the removal of the binder material. The PS binder system is compared with conventional binder system based on the physical and mechanical properties of Inconel718 sintered parts. It was found that the PS binder systems proved to enhance the properties and improve the microstructure behaviour. Result shows that the sintered properties from palm oil binder system can be achieved in accordance to the Metal Powder Industries Federation standard.

Influence of palm stearin on powder injection moulding of stainless steel 316L

The palm oil derivative, palm stearin (PS) has been formulated and evaluated as a possible alternative binder system. Palm stearin content can be an advantage during the debinding process because the components have different melting points. It is important that the removal of binder must be performed gradually to maintain the shape of the debound part. At different heating temperatures, the binder content melts, leaving different impurities at different melting points. The remaining impurities help to form capillary holes for the removal of the following binder material. The PS binder system is compared with conventional binder systems based on the physical and mechanical properties of stainless steel 316L sintered parts. It was found that PS binder systems enhanced the properties and fulfilled the Metal Powder Industries Federation Standard 35 for powder injection moulding part.

Unique values win PM design awards

Innovation, superior engineering, market viability and sustainability were distinguishing features of the 2011 winners of the Design Excellence awards, sponsored by the Metal Powder Industries Federation (MPIF) and presented at PowderMet. Ken Brookes looks at the award-winning products.

Injection Molding of Titanium Alloy Implant For Biomedical Application Using Novel Binder System Based on Palm Oil Derivatives

Problem statement: Titanium alloy (Ti6Al4V) has been widely used as an implant for biomedical application. In this study, the implant had been fabricated using high technology of Powder Injection Molding (PIM) process due to the cost effective technique for producing small, complex and precision parts in high volume compared with conventional method through machining. Approach: Through PIM, the binder system is one of the most important criteria in order to successfully fabricate the implants. Even though, the binder system is a temporary, but failure in the selection and removal of the binder system will affect on the final properties of the sintered parts. Therefore, the binder system based on palm oil derivative which is palm stearin had been formulated and developed to replace the conventional binder system. Results: The rheological studies of the mixture between the powder and binders system had been determined properly in order to be successful during injection into injection molding machine. After molding, the binder held the particles in place. The binder system had to be removed completely through debinding step. During debinding step, solvent debinding and thermal pyrolysis had been used to remove completely of the binder system. The debound part was then sintered to give the required physical and mechanical properties. The in vitro biocompatibility also was tested using Neutral Red (NR) and mouse fibroblast cell lines L-929 for the direct contact assay. Conclusion: The results showed that the properties of the final sintered parts fulfill the Standard Metal Powder Industries Federation (MPIF) 35 for PIM parts except for tensile strength and elongation due to the formation of titanium carbide. The in vitro biocompatibility on the extraction using mouse fibroblast cell line L-929 by means of NR assays showed non toxic for the sintered specimen titanium alloy parts.

Sinterização de uma mistura de cavaco de aço inoxidável com pó do mesmo material: uma nova tecnologia para a reciclagem de metais?

A reutilização dos materiais recicláveis tem como principais objetivos minimizar os impactos ambientais e racionalizar a utilização das cadeias energéticas, sendo que essa prática deverá, com toda a certeza, ser cada vez mais implementada à medida que o mundo moderno avança. No presente trabalho, foram sinterizadas amostras de misturas de cavacos de aço inoxidável da série 316, com pó do mesmo material. Nesse caso, a porcentagem de cavaco variou de zero a 25% em peso, de 5 em 5%. Após a compactação, na pressão de 600MPa, as amostras foram sinterizadas todas elas ao mesmo tempo, numa só fornada na temperatura de 1473 K. O comportamento mecânico do produto final foi avaliado através de Ensaios de Ruptura Transversal recomendados e normalizados pela MPIF - Metal Powder Industries Federation e pela ASTM. As análises efetuadas pela Metalografia Quantitativa Convencional das amostras sinterizadas demonstraram regiões de intensa difusão, portanto regiões de sinterização de longo alcance. A resistência mecânica dos corpos-de-prova foi comparada com a resistência mecânica do aço inoxidável sinterizado, sem cavaco. Os resultados obtidos foram muito acima do esperado, demonstrando a viabilidade desse novo procedimento.

Improved homogenization of Ni in sintered steels through the use of Cr-containing prealloyed powders

The homogenization of Ni in powder metal (PM) steel compacts is usually difficult even after high-temperature sintering at 1250°C. An earlier study by the authors demonstrated that this problem can be alleviated through the addition of 0.5 wt pct Cr in the form of stainless steel powders. To further improve the microstructure and mechanical properties of Ni-containing PM steels and to understand the mechanisms, an attempt was made in this study using the Fe-3Cr-0.5Mo prealloyed powder as the base material. The results showed that the distribution of the Ni additives was significantly improved. As a result, the tensile strength of the Fe-3Cr-0.5Mo-4Ni-0.5C compact sintered at 1250°C reached 1323 MPa. The elongation was higher than 1 pct. These sinter-hardened properties, which were attained using a slow furnace cooling rate, were comparable to those of the sinter-hardened alloys reported in the literature using accelerated cooling and were equivalent to those of the best quenched-and-tempered alloys registered in the Metal Powder Industries Federation (MPIF) standards. These improvements were attributed to the positive effect of Cr addition on alloy homogenization due to the reduction of the repelling effect between Ni and C, as was demonstrated through the thermodynamic analysis using the Thermo-Calc program.

Improvements in microstructure homogenization and mechanical properties of diffusion-alloyed steel compact by the addition of Cr-containing powders

The use of diffusion-alloyed powders for fabricating powder metal parts, despite alleviating the segregation problem of the alloying elements while retaining good compressibility, still cannot attain homogeneous microstructure in as-sintered products. The presence of soft Ni-rich areas and pores causes poor mechanical properties compared to those of wrought steel counterparts. This study investigated the effects of adding 0.5 wt pct Cr, which was introduced in the 316L stainless steel powder form, on the microstructure and mechanical properties of diffusion-alloyed Fe-4Ni-1.5Cu-0.5Mo-0.5C (Metal Powder Industries Federation (MPIF) FD-0405) steels. The results show that weak Ni-rich areas were present in the Cr-free specimen when sintered at 1120 °C and 1250 °C. These areas were lean in carbon because of the strong repelling effect between Ni and C. With the addition of 316L powders, the Cr was uniformly distributed and helped eliminate the soft Ni-rich areas, particularly in specimens sintered at 1250 °C. The distribution of carbon also improved. With a more uniform distribution of Ni and C, and more homogeneous microstructure, which consisted mainly of bainite and martensite, the mechanical properties of the Fe-4Ni-1.5Cu-0.5Mo-0.5C diffusion alloy steels were improved significantly.

Impact properties of sintered and wrought 17–4 PH stainless steel

Charpy V notch (CVN) impact testing was conducted on full size and subsize specimens of sintered and wrought 17–4 PH stainless steel (17–4 PH SS) in the as sintered and H900 heat treated conditions. Test geometries correspond to the American Society for Testing and Materials (ASTM) and Metal Powder Industries Federation (MPIF) impact testing standards. Merits of a notched specimen compared with an unnotched specimen were analysed for both the wrought and sintered materials. The notched ASTM standard bars had a lower coefficient of variance for impact energy than the unnotched MPIF standard bars and displayed greater toughness. Porosity and grain size have a detrimental synergistic effect on impact toughness for the sintered material. Following a discussion about the differences in the wrought and sintered microstructures, it is recommended that impact testing of the injection moulded and sintered specimens should be evaluated according to the ASTM test specifications.

Micro powder injection moulding

Powder injection molding (PIM) has emerged as a viable method for producing complex shaped parts at a competitive cost. The PIM process, which consists of feedstock preparation, injection molding, debinding and sintering, uses a combination of powder metallurgy and plastic injection molding technologies to produce net-shape metal, ceramic or hard materials components [R.M. German, A. Bose, Injection Molding of Metals and Ceramics, Metal Powder Industries Federation, Princeton, NJ 1997]. Using very fine powders and a modified feedstock and injection process, PIM can also be applied to microstructures and microcomponents (micro PIM). In this study, ceramic microcomponents of alumina (Al 2O 3) were produced and analyzed. It was shown that the smallest achievable structures were about ten times the particle size. For example, with 400 nm alumina particles, structures of 5 μm were successfully injection molded and sintered. As a wide variety of metals and ceramics can be processed, including functional and catalytic materials, micro PIM opens up new avenues for the mass production of microcomponents for the medical and automotive industries and for applications in (bio)chemistry and sensor technology.

Book Review: Powder Metallurgy and Particulate Materials Processing: The Processes, Materials, Products, Properties, and Applications

Powder Metallurgy and Particulate Materials Processing: The Processes, Materials, Products, Properties, and Applications, by R.M. German. Princeton, NJ, Metal Powder Industries Federation, 2005. ISBN: 0-9762057-1-8

Powder forged or C-70 steel? Now the MPIF strikes back

In the past 20 years powder forging has established a solid leadership in the US over rival forging methods for manufacturing internal combustion engine connecting rods. PF is gaining ground in other major markets such as Europe. But last year the American Iron and Steel Institute threw a rock into the calm pond of assumption, claiming a study at Toledo University showed that C-70 forging steel offered advantages over PF. Members of the Metal Powder Industries Federation were stung into action, refuting the AISI's claims in this MPIF White Paper by Jim Dale…

Design competition opens

The Metal Powder Industries Federation (MPIF) has opened the 2004 International PM Design Competition. Entries must be received by 27 February. The competition recognises outstanding achievements in the commercial production of PM components. This is a short news story only. Visit www.metal-powder.net for the latest powder metallurgy industry news.

PM's part in defence

A two-day seminar on powder metallurgy in defence-related industries is to be staged by the Metal Powder Industries Federation in Baltimore later this month. The aim of the seminar is to set out the benefits for companies in gaining government contracts. This is a short news story only. Visit www.metal-powder.net for the latest powder metallurgy industry news.

‘We’re moving on and up towards ambitious targets’

The powder metallurgy industry in the US remains ’strong and agile’. That’s the view from the top of the North American industry association, the Metal Powder Industries Federation…

Quality ambition?

Commitment to quality is firmly at the top of the agenda for the powder metal industry and no one that attended the PM 2TEC Conference and Exhibition in Las Vegas will have been left in any doubt of it. David Schaefer, President of the Metal Powder Industries Federation, probably came somewhere near the bull's eye when he told the conference that long-term quality and durability of parts are essential. However, it has to be said that automotive PM users have been unequivocally clear in the past year that an unrelenting emphasis on quality is basic to the future progress of the PM industry.

Effects of sintering atmosphere on the microstructure and mechanical property of sintered 316L stainless steel

In the present work, N2, N2 + H2, Ar and Ar + H2, were used as the sintering atmosphere of Metal Injection Molded 316L stainless steel respectively. The influences of the sintering atmospheres on C, O, N contents of the sintered specimens, sintered density, grain morphology and mechanical properties were investigated. The results show that C, O, N contents of the sintered specimens can be controlled in permitted low values. The ultimate tensile strength and elongation of the specimen sintered in N2 + H2 atmosphere are 765 MPa and 32% respectively. Using Ar and Ar + H2 as the sintering atmosphere, the density of the sintered specimens is 98% of the theoretical density; the pores are uniformly distributed as small spherical shape and the grain size is about 50 µm. The mechanical properties of the specimen, i. e. ultimate tensile strength 630 MPa, yield strength 280 MPa, elongation 52%, HRB 71, are much better than those of the American Metal Powder Industries Federation (MPIF) 35 Standard after being sintered in Ar + H2.

射出成形 米国ＭＩＭ市場の現況

It is said that there are more than 40 MIM (Metal Injection Molding)-related companies in America. Aiming at the diffusion of MIM, 21 of these companies have formed and are members of an organization called MIMA (Metal Injection Molding Association). MIMA is one of the lower branches of MPIF (Metal Powder Industries Federation). Among MIMA member companies, there are MIM parts producers; powders, binders and feedstock suppliers; and MIM machine, debinding and sintering equipment suppliers. Last year, MIMA sent out a questionnaire to each of its member companies to inquire into the present conditions and future prospects of the MIM business, problems that hinder the diffusion of MIM, measures to be taken in order to achieve diffusion, etc. The results, which were totaled and released to member companies last year in October, indicated that most of the companies believed that a lack of educational campaigns aimed at part designers, who are MIM customers, was impeding MIM diffusion. At present, since it is also believed in Japan that the achievement of diffusion of MIM technology depends on the improvement of the understanding level of part designers, JSPM (Japan Society of Powder and Powder Metallurgy) and JPMA (Japan Powder Metallurgy Association) have begun to take measures aiming at MIM standardization and educational campaigns. We have the impression that the problems confronting MIM are the same around the world. The findings of this survey provide very interesting hints, and we believe that they will be a good reference for the development of MIM technology in our country.

Part winners represent new markets for PM

From adjustment gears for sprinkler systems to surgical scissors, from latchbolts to parking gears, the winners of the Metal Powder Industries Federation's (MPIF) 1998 part-of-the-year design competition represent further market breakthroughs for powder metallurgy (PM). The winning parts show successful conversions from malleable iron, plastic injection moulding, investment casting, forging, die casting and machining, with significant cost savings and enhanced design complexity.