Powder Metal Parts Research Articles

Effect of Porosity Content on the Weldability of Powder Metal Parts Produced by Friction Stir Welding

Friction stir welding technique (FSW) has many advantages in terms of tool design, rotational speed and traveling speed, and can be adjusted in a precise manner. It enables heat input into the system to be controlled. In this study, Aluminum powders were compacted at 350,400 and 450 MPa pressure and sintered at 450 oC temperature for 30 minutes in Ar atmosphere. Sintered powder metal parts were joined to each other by FSW at the speed of 1800 rpm and traveling welding speed 200 mm/min under a constant friction force. The results show that the amount of porosity affects the weldability of powder metallurgy (P/M) parts. Furthermore, the porosity and microstructural evolution of the Aluminum also affected the hardness values of the tested materials.

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.

‘More power’ call sparks soft compact research

The 42-volt electrical system is to be introduced in automobiles to provide the extra power needed for various electromagnetic devices. This offers an opportunity for insulated iron powder to replace lamination steel in a variety of motors. Brushless motor design can probably benefit most from insulated iron powder compacts because of the design simplicity of powder metal parts and three-dimensional flux capability that is most beneficial in rotating devices says Sim Narasimhan…

Development of a powder warming compacting machine with an electrical heating system

Density control is an important factor in producing high-quality powder metallurgy parts (P/M). All mechanical properties are improved with increased density. To obtain parts with higher density, the double-pressing, double-sintering, and powder forging or copper infiltration methods are usually applied. However, the operation cost also increases from 40% to 100%. Recently, suppliers of P/M material and compacting presses have cooperated to develop warm compacting technology that increases the density of powder metal parts from 7.1 to 7.2–7.5 g/cm 3 with a single press and single sintering cycle while keeping the operation cost increase below 20%. This paper presents a new powder heating method with an electrical heater element instead of the hot oil circulation process that is currently used in warm compaction. This electrical heating system simplifies the heating element installation and can be fitted to all types of presses. This system is easy to maintain and operate, and could significantly reduce production costs.

Densification of nano-crystalline titania powder compacts : H.G.Kim, K.T.Kim. (University of Science and Technology, Pohang, Korea.) Acta Mater., vol 47, no 13, 1999, 3561–3570

Electromagnetic processing was used to study the effects of electro-magneto forming on the dimensional control and thermal stability of sintered powder metal (PM) parts. The investigation was carried out on sinter-hardened, low chromium-molybdenum bainitic steel. The results show an increase in the microhardness of about 14% for the electromagnetic processed parts compared to the as-sintered parts. This was attributed to the 2% increase in the density, 17% and 29% reduction in the volume fraction of porosity and width of the bainitic lath, respectively, due to the electromagnetic processing. Dimensional characterization was carried out using a vertically aligned push-rod dilatometer. After four thermal cycles of heating and cooling, at a controlled rate of 5 °C/min to 1000 °C, the electromagnetic processed parts exhibited reduced dimensional change of about 44% lower than for the as-sintered parts. This is significantly important for applications that demand high dimensional tolerance and performance, especially at elevated temperatures.

Modelling the relationship between process parameters and mechanical properties using Bayesian neural networks for powder metal parts

A neural network based system is presented in this paper for modelling mechanical behaviour of powder metal parts as a function of processing conditions. The neural network selection is made using a Bayesian framework, which enables prediction of mechanical properties to be made, indicating a level of confidence in the result. The system gives good prediction accuracy for a number of commercially available ferrous powder materials; the performance for two different powder grades is reported. In order to select process parameters that meet the required mechanical properties for the part, a prototype process 'advisor' is developed using these neural network models. Three different neural networks are trained to predict tensile strength, elongation and hardness for ferrous powder grades, and are used in the process 'advisor' to recommend suitable process parameters.

Effects of manufacturing processes on properties of high density powder metal parts: Y. Trudle, M. Gagne (Quebec Metal Powders Ltd, Montreal, Canada)

Effects of manufacturing processes on properties of high density powder metal parts: Y. Trudle, M. Gagne (Quebec Metal Powders Ltd, Montreal, Canada)

Injection moulding used to produce powder metal parts

Injection moulding used to produce powder metal parts

Corrosion and Protection of Sintered Metal Parts

An analysis of the mechanism of corrosion and protection of sintered powder metal parts reveals that the role of surface pores is an unusual and incompletely understood characteristic. Electrochemical principles can be enunciated and interpreted in the context of pores, which may or may not be interconnected throughout the structure, and models can be proposed on the basis of well-known metallographic features. In these models the main bulk surface may be assumed to be covered with an oxide film and acts as cathode with respect to the pores themselves which are relatively anodic and therefore corrosion sites. Any protective mechanism must therefore be primarily concerned with the elimination of pores by sealing, several processes being available for this stage. Subsequent coating may then be directed towards galvanic protection rather than the micro-throwing power problems of filling the pores.

Plant for the manufacture of powder metal parts for instruments

Plant for the manufacture of powder metal parts for instruments