Effect of solution annealing and precipitation hardening at 250 °C–550 °C on microstructure and mechanical properties of additively manufactured 1.2709 maraging steel

Ludmila Kučerová,Štěpán Jeníček,Karolina Burdová,Iveta Chena

doi:10.1016/j.msea.2021.141195

Ludmila Kučerová, Štěpán Jeníček + Show 2 more

Open Access

https://doi.org/10.1016/j.msea.2021.141195

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Abstract

Post-processing heat treatment of additively manufactured (AM) maraging steel is an important issue in the tailoring of the final mechanical properties of a product. Up to now, mainly precipitation hardening at temperatures of 450 °C–500 °C has been studied either in as-built or solution-annealed samples. This work, however, presents an overview of the effect of much broader tempering temperatures of 250 °C–550 °C on the microstructure and mechanical properties of as-built maraging steel. Furthermore, the effect of previous solution annealing of AM steel at a lower temperature of 820 °C and at a higher temperature of 940 °C on subsequent precipitation hardening is also described. The results obtained for the precipitation behaviour of AM maraging steel are compared with those of conventionally produced maraging steel. The microstructure and mechanical properties of AM samples pre-annealed at 940 °C and precipitation hardened were found to be comparable to the conventionally processed reference sample at all hardening temperatures. On the other hand, the microstructures and properties of AM samples pre-annealed at 820 °C and precipitation hardened strongly resembled the results of as-built samples. However, even after a 6-h hold at the highest tempering temperature of 550 °C, distinct differences could still be found in the samples prepared with various initial conditions.

Highlights

Maraging steels are widely used in high-performance military, aerospace, automobile, tool and die applications [1,2,3,4,5,6,7,8]
The same precipitation hardening heat treatment was applied to maraging steel prepared in four different initial conditions
These conditions were as follows: additively manufactured as-built condition, additively manufactured and solution annealed at 820 ◦C, additively manufactured and solution annealed at 940 ◦C, and conventionally manufactured steel under the Vaco brand name in the solution-annealed condition

Summary

Introduction

Maraging steels are widely used in high-performance military, aerospace, automobile, tool and die applications [1,2,3,4,5,6,7,8]. Maraging steels are suc cessfully used in tooling, as moulds for plastic injection and tools for die casting magnesium, zinc or aluminium alloys [9,10]. These applications are enabled by their suitable properties, mainly good toughness, and high resistance to crack propagation and thermal fatigue [9]. Lower thermal expansion along with good thermal conductivity reduce the surface temperatures under thermal loads, which results in lower thermal stresses [13,14]

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