Capsule-free hot isostatic pressing of sintered steel to full density using water atomised iron and Cr-alloyed powder consolidated by cold isostatic pressing

Powder metallurgy (PM) steel with enhanced density is essential for meeting the demands on high strength and high-performance applications. In this study, cold isostatic pressing (CIP) is applied for consolidating water-atomised iron and Cr-alloyed steel powder to reach about 95% densification before sintering. Additionally, the effect of the lubricant and graphite addition on the compressibility of the different base powder types was evaluated. The maximum green densities of approximate to 7.55 g cm(-3) for iron powder and approximate to 7.45 g cm(-3) for Cr-alloyed powder were reached after CIP at 800 MPa. The sintering at 1250 degrees C with added graphite allowed to achieve increased densification to approximate to 7.60 g cm(-3) for the iron and approximate to 7.50 g cm(-3) for Cr-alloyed grades, respectively. These levels were sufficient for surface pore closure, which allowed the application of the capsule-free hot isostatic pressing (HIP) after sintering to reach full density. This approach paves the way for manufacturing large-sized PM components.

Automated summary

This study utilized cold isostatic pressing to consolidate water-atomised iron and Cr-alloyed steel powder, reaching high densities before sintering, and further increasing densification post-sintering with the addition of graphite, paving the way for manufacturing large-sized PM components.