Influence of Various Process Parameters on the Density of Sintered Aluminium Alloys

This paper presents the results of density measurements carried out on Alumix sintered parts. ECKA Alumix aluminium powders were used because of their wide application in the powder metallurgy industry. The compacts were produced using a wide range of compaction pressures for three different chemical compositions. The compacts were then sintered under a pure dry nitrogen atmosphere at three different temperatures. The heating and cooling rates were the same throughout the entire test. The results showed that the green density increases with compaction pressure, but that sintered density is independent of green density (compaction pressure) for each sintering temperature

Influence of the Amount of Master Alloy on the Properties of Austenitic Stainless Steel AISI 316L Powder Sintered in Hydrogen

AISI 316L austenitic stainless steel powder was modified with four different amounts of boron (0.1; 0.2; 0.3; 0.4 of wt. %) in the form of MasterAlloy micro-powder, and was sintered in a pure dry hydrogen atmosphere in order to obtain high density sintered samples characterized by a thickened non-porous surface layer. We investigated the influence of the amount of boron on: density, hardness, grain microhardness, porosity, microstructure and surface quality. The study revealed that it is possible by a conventional compacting and sintering process to obtain near full-density sintered samples with a non-porous superficial layer without boride precipitations

Microstructure and properties of sintered 410L steel with copper addition

In the present study copper modificated 410L stainless steel was investigated. This steel was fabricated based on powders, by the pressing and sintering. By varying amount of copper and sintering temperature the properties of the 410L stainless steel can be improved. At sintering temperature of 1240°C and at high copper levels the microstructure of steel is predominately martensitic. The sintered density of steel increases as the copper level increases, with a drop-off in density at 4 w/o Cu. It has been shown that stainless steels with higher copper levels have higher hardness and better density in comparison to steels sintered in 1260°C. In general, higher sintering temperature and low copper levels favor the formation of ferrite. An examination of the microstructures of these steels reveals that they are a mixture of ferrite and martensite

AISI 316L-hydroxyapatite sintered composite biomaterials

The combinations of good biocompatibility of hydroxyapatite and good mechanical properties of 316L steel should lead to obtain better biomaterial. 316L-hydroxyapatite composites were produced by the PM technology. Microstructure and properties of these materials were affected by chemical composition of powders mixture and sintering temperature. Sintering temperature of 1240°C and hydroxyapatite addition of 3 wt. % provide to obtain the best density and hardness sintered 316L-hydroxyapatite compositions

Article Improving the Dimensional Stability and Mechanical Properties of AISI 316L + B Sinters by Si3N4 Addition

The following paper describes a new and effective method to obtain high-density sinters with simultaneously decreased distortions, produced by one press and sinter operation. This effect was achieved through the induced disappearance of the eutectic liquid phase. The study was carried out on AISI 316L stainless steel powder that was mixed with elemental boron and silicon nitride. Boron was used as a sintering process activator. The scientific novelty of this publication consists of the use of a silicon nitride as a solid-state nitrogen carrier that was intended to change the borides’ morphology by binding boron. Based on the thermodynamic calculations, 20 blends of various compositions were tested for physical properties, porosity, microstructure, and mechanical properties. Moreover, phase compositions for selected samples were analyzed. It was shown that the addition of silicon nitride as a nitrogen carrier decreases the boron-based eutectic phase volume and both increases the mechanical properties and decreases after-sintering distortions. An explanation of the observed phenomena was also proposed

Influence of Sintering Atmosphere, Temperature and the Solution-Annealing Treatment on the Properties of Precipitation-Hardening Sintered 17-4 PH Stainless Steel

So far, unlike metal injection molding (MIM), conventional powder metallurgy technology (PM) has not been regarded as a method for producing structural elements from 17-4 PH powders, due to the problems of obtaining almost fully compacted shapes after sintering. Nevertheless, recent research demonstrates that it is possible to manufacture sintered parts with high strength by pressing and sintering. The purpose of the study was to determine the degree of densification of 17-4 PH sintered stainless steel during sintering at different temperatures and atmospheres. As a result of the study, it was pointed out that both the temperature and the sintering atmosphere play an essential role in the process of densification of the studied powders during sintering. The formation of delta ferrite and a more pronounced degree of spheroidization of the pores is activated by a higher sintering temperature. Furthermore, after solution-annealed and age-hardened treatment, sintered 17-4 PH stainless steel exhibits high strength with moderate ductility at a level that is difficult to achieve for other sintered stainless-steel grades, such as austenitic, ferritic and martensitic. In turn, the largest improvement in the pitting corrosion resistance in 0.5 M NaCl solution is reached by sintering at 1340 °C in hydrogen and after solid solution treatment

The Effect of Nitrogen Linear Flow on Lubricant Removal and Sintering Densification of Alumix 431D Grade Powder

ECKA Granules Alumix 431D commercial grade, press ready, pre-alloyed aluminium-based powder containing 1.5 mass% of Acrawax C was used to study the effect of nitrogen linear flow on de-lubrication and sintering densification. In situ dimensional changes were controlled by dilatometry. Microstructural observations of sintered compacts were also performed. The results clearly showed the strong influence of nitrogen linear flow on de-lubrication, and thus on the sintering behaviour of the examined powder. High nitrogen linear flow is required to produce the desired sintered microstructure—characterised by residual porosity. In contrast, at low nitrogen velocity, the lubricant removal is not complete, which in turn significantly impedes densification

The Influence of Nanographite Addition on the Compaction Process and Properties of AISI 316L Sintered Stainless Steel

This paper presents the effect of graphite addition on the pressing process and selected mechanical properties of AISI 316L austenitic stainless steel. The graphite powders used in this study differed in the value of the specific surface area of the particles, which were 15 (micropowder), 350, and 400 m2/g (nanopowder). Mixtures with the addition of lubricants—stearic acid and Kenolube—were also created, for comparison purposes. The scope of the tests included compressibility of blends, measurements of the ejection force while removing the compacts from the die, micro-structural studies, a static tensile test, a three-point bending test, a Kc impact test, Rockwell hardness, and Vickers microhardness measurements. The study demonstrated that the addition of graphite nanopowder to the studied steel acts as a lubricant, providing a significant improvement in lubricity during the pressing process. Moreover, the addition of nanographite allowed for a significant increase in the mechanical properties studied in this work; it was observed that, for the sinters made of mixtures with a higher graphite content and with a large specific surface area of its particles, better values for the tested properties were obtained