Novel Approaches for achieving fully dense powder metallurgy steels

​Maheswaran Vattur Sundaram, Materials and manufacture IMS,  defends his doctoral thesis on March 29.

Opponent: Professor Mónica Campos, Universidad Carlos III de Madrid, Madrid, Spain
Supervisor: Eduard Hryha, IMS
Examiner: Lars Nyborg, IMS

Doctoral thesis defence Maheswaran Vattur Sundaram 
2019-03-29 10:00
Virtual Development Laboratory (VDL)
Chalmers Tvärgata 4C​

Popular description
From a historical perspective, utilising metal powder for making goods, monuments and jewellery were adopted as early as 3000 BCE by Egyptians; Inca’s used gold powder for making ornaments and the Iron pillar in Delhi, India, was made using reduced iron ore by hammering and it exists even today as a standing monument. However, powder metallurgy as an industrial process has grown rapidly only within the last century. Earlier development was focused on tungsten filaments as it was not possible to process tungsten through other methods due to the high melting point. Manufacturing steel parts or components from metal powders has grown in the beginning of the 20th century. Powder metallurgy, as a metal forming technique, utilises raw material in the form of powder particles, which are shaped into desired form using die-tools by pressing at high pressures. Once shaped, they are heated in a furnace to form metallic bonds, to provide the necessary strength to the component which is called sintering. Further, utilising metal powder for manufacturing conserves raw material, as it is consumed only for the desired shapes. Moreover, the energy required to make a steel component using press and sinter route is much lower than the other manufacturing processes such as casting, forging, and machining. This makes it very much attractive for using this process route for the mass production of components. 
However, the main drawback of this approach is the inability to reach full density, which limits the application of these materials. It is established that the properties of materials are a direct function of density; hence, increasing the density increases the properties and thus its potential applications. Therefore, the main focus of this study is to find the possible ways to reach full density in powder metallurgy steels, such that the process can be directly implemented for manufacturing. To do so, different processes utilising pressure, temperature, and combination of both were evaluated utilising low-alloyed steel powder. The challenges associated with powder processing at different stages were also addressed. From the results, it was demonstrated that full densification can be achieved through the proposed approaches based on the requirements. Hence, with this immense potential, these approaches provide opportunities for continuous progress of powder metallurgy in the future.

Published: Wed 06 Mar 2019. Modified: Thu 07 Mar 2019