Hot Deformation Behavior of an Ultra-High-Strength Fe–Ni–Co-Based Maraging Steel

Abstract

Hot processing behavior of an ultra-high-strength Fe-Ni-Co-based maraging steel was studied in temperature range of 900-1200 °C and strain rate range of 0.001-10 s −1 . Deformation processing parameters and optimum hot working window were characterized via flow stress analysis, constitutive equation construction, hot processing map calculation and microstructure evolution, respectively. Critical strain value for dynamic recrystallization was determined through theoretical mathematical differential method: the inflection point of θ-σ and − ∂θ/∂σ − σ curves. It was found that the flow stress increased with the decrease in deformation temperature and increase in the strain rate. The power dissipation maps in the strain range of 0.1-0.6 were entirely similar with the tendency of contour lines which implied that strain had no strong effect on the dissipation maps. Nevertheless, the instability maps showed obvious strain sensitivity with increasing strain, which was ascribed to the flow localization and instability. The optimized hot processing window of the experimental steel was obtained as 1100-1200 °C/0.001-1 s −1 and 1000-1100 °C/0.001-0.1 s −1 , with the efficiency range of 20-40%. Owing to high Mo content in the experimental steel, high dynamic activation energy, Q = 439.311 kJ mol −1 , was achieved, indicating that dynamic recrystallization was difficult to occur in the hot deformation process, which was proved via microstructure analysis under different hot deformation conditions.

Hot Deformation Behaviour of Additively Manufactured 18Ni-300 Maraging Steel

“…It is apparent that the calculated here activation energy value for AM 18Ni300 steel is similar to that of conventionally manufactured M300 grade (391 kJ/mol) [ 19 ], M350 grade (371 kJ/mol) [ 20 ] and is much lower than that of CF250 grade (458.8 kJ/mol) [ 27 ] in magnitude. Further, the activation energy value for AM 18Ni300 value is much larger than the values for self-diffusion in γ-iron ( Q = 280 kJ mol −1 ), implying that dynamic recovery and dynamic recrystallization are the dominant mechanisms instead of diffusion during hot deformation [ 28 ]. It is also worth noting that the calculated Q value for the maraging steel AM 18Ni-300 is similar to that of the conventionally produced grade M300 ( Q = 390 kJ mol −1 ) [ 19 ].…”

Microstructure Evolution and Deformation Behavior of High Strength Titanium Clad Steel Plate in the Thermal Compression

“…The dislocation density progressively increased during deformation, leading to the creation of a substructure and resulting in material softening. [20] The dynamic recovery (DRV) was caused with substructure and deformation increasing, [21,22] and the relationship between substructure and strain rate [23][24][25] is expressed as Equation ( 1)…”

Influence of Cold Spray Parameters on Bonding Mechanisms: A Review

“…However, low melting point materials such as aluminium start sticking at the nozzle's throat after an inevitable rise in the process gas temperature, leading to nozzle clogging and an undesirable decrease in deposition efficiency. Therefore, the upper limit of the temperature for attaining maximum particle velocity without nozzle clogging depends on the feedstock properties [81][82][83][84]. The optimum gas temperature for each material category to avoid nozzle clogging is a subject for further investigations.…”

“…An increase in pressure of the process gas increases the acceleration rate of the particles in the nozzle, enabling the particles to attain significantly high velocities before leaving the nozzle [81]. Therefore, an increase in pressure of the process gas yields high energy impact of particles at the substrate, which enhances mechanical interlocking and promotes metallurgical bonding at the particle-substrate and particle-particle interfaces [82]. Furthermore, higher energy impact results in deeper penetration of the particles into the substrate and the consecutive layers.…”