Case History – AGI Impeller for Hydraulic Pumps

This case describes a technological upgrade project based on the application of an austempering heat treatment to an impeller made of EN‑GJL‑200 grey cast iron.

The impeller analyzed is part of a drainage pump used in the construction, mining, and agricultural sectors.

EN‑GJL‑200 grey cast iron has long been a benchmark material thanks to its excellent castability and outstanding machinability. These characteristics make it particularly suitable for manufacturing components with complex geometries, such as pump casings and drainage pump impellers. From a performance standpoint, its mechanical properties fully meet the requirements of standard-duty applications, ensuring reliable operation when pumping clear water, lightly contaminated wastewater, and non-aggressive industrial liquids.

However, when operating conditions become more severe, the material’s limitations emerge. In pumping systems handling abrasive fluids, EN‑GJL‑200 does not provide sufficient wear resistance: the impeller blades are subject to premature wear in the presence of suspended solid particles, progressively compromising efficiency and operational continuity. In such scenarios, the standard-duty configuration is unable to guarantee long-term, reliable performance.

Heat treatment as a solution

This led to the need for a material upgrade for heavy-duty applications, capable of combining higher mechanical strength, extended service life, and stable performance, even in harsh and highly abrasive environments.

Within this context, the customer selected the austempering heat treatment, transitioning from conventional grey cast iron to Austempered Grey Iron (AGI), specifically grades AGI 270 and AGI 350. This strategic choice made it possible to significantly increase wear and fatigue resistance, extending component service life and ensuring consistent performance under high mechanical loads.

Adopted Solution: Performance Upgrade Without Redesign

The developed solution enabled a significant improvement in the performance of the standard GJL200 component while maintaining an extremely limited economic impact.

This result was achieved by fully preserving the original EN‑GJL‑200 grey cast iron casting and applying an austempering heat treatment to the machined impeller prior to assembly.

The intervention required no changes to foundry tooling and no modifications to the existing machining line, ensuring seamless integration into the established production process.

This approach allowed for a targeted and effective performance upgrade, avoiding a complete component redesign and eliminating the need for new tooling investments, with clear benefits in terms of cost, lead time, and production continuity.

Results Achieved

The upgrade delivered a tangible improvement in performance, with specific advantages in mechanical, functional, production, and economic terms.

Mechanical Performance

Increased hardness: +45% in AGI270 grade, +100% in AGI350 grade), without compromising toughness

Economic Benefits

Alternative solutions, such as steel, would have required significant investments and complex production cycles; AGI proved to be the simplest and most cost-effective solution.

Time-to-market

  • Quick upgrade because it does not require redesign
  • Easier validation: geometry and interfaces unchanged
  • Reduce industrialization and release times

Functional Benefits for the Impeller

  • Improved resistance to abrasive fluids
  • Extended pump service life
  • Reduced maintenance requirements

Production Benefits

  • No changes to castings or patterns
  • No changes to machining operations
  • No substantial modifications to production cycles

Conclusions

The upgrade of the impeller from EN-GJL-200 to Austempered Grey Iron (AGI) represents a concrete example of how austempering heat treatment applied to grey cast iron can:

  • Increase mechanical performance
  • Eliminate redesign costs and engineering risks
  • Improve reliability and operational service life
  • Preserve the existing production process

This case confirms the potential of AGI as a strategic material solution for applications requiring enhanced wear resistance without compromising manufacturing efficiency.

Another example of a hydraulic pump impeller in AGI

Case History

Real cases explaining the development of client projects