Characterization of Aging Behavior in M250 Grade Maraging Steel Using Ultrasonic Measurements

Abstract

Ultrasonic measurements have been carried out in M250 grade maraging steel specimens subjected to solution annealing at 1093 K for 1 hour followed by aging at 755 K for various durations in the range of 0.25 to 100 hours. The influence of aging on microstructure, room temperature hardness, and ultrasonic parameters (longitudinal and shear wave velocities and Poisson's ratio) has been studied in order to derive correlations among these parameters in aged M250 maraging steel. Both hardness and ultrasonic velocities exhibit almost similar behaviors with aging time. They increase with the precipitation of intermetallic phases, Ni 3 Ti and Fe 2 Mo, and decrease with the reversion of martensite to austenite. Ultrasonic shear wave velocity is found to be more influenced by the precipitation of intermetallic phases, whereas longitudinal wave velocity is influenced more by the reversion of martensite to austenite. Unlike hardness and ultrasonic velocities, the Poisson's ratio exhibits a monotonous decrease with aging time and, hence, can be used for unambiguous monitoring of the aging process in M250 maraging steel. Further, none of the parameters, i.e., hardness, ultrasonic velocity, or Poisson's ratio, alone could identify the initiation of the reversion of austenite at early stage; however, the same could be identified from the correlation between ultrasonic velocity and Poisson's ratio, indicating the advantage of using the multiparametric approach for comprehensive characterization of complex aging behavior in M250 grade maraging steel.

Effect of Cyclic Aging on Mechanical Properties and Microstructure of Maraging Steel 250

“…These steels are classified as materials of ultrahigh strength combined with good toughness (Ref [1][2][3][4], which maintain their properties at temperatures up to at least 623 K. As such, they constitute an alternative to hardened carbon steels in critical applications where high strength and good toughness and ductility are required. They harden by a simple and relatively low-temperature maraging treatment at 753 K for 3-8 h followed by air cooling (Ref 5,6).…”

Ultrasonic Characterization of Aging Behavior in M250 Grade Maraging Steel

“…In addition, they hinted that the increase in the sound velocity might be related to the Young's moduli increase due to Ni and Ti depletion. [12] Their main findings were as follows.…”

“…[11] Recently, Rajkumar et al studied the aging of 250 maraging steel (M250) using an ultrasonic method together with TEM. [12] In their study, they tried to correlate the time variations in the longitudinal sound velocity, V L , and in the transverse (shear) sound velocity, V T , with microstructural and hardness changes. In their study, aging took place at 755 K between 0.25 and 100 hours.…”

“…In their study, aging took place at 755 K between 0.25 and 100 hours. [12] Rajkumar et al attributed the increase in hardness and sound velocities to the formation of Ni 3 Ti and Fe 2 Mo precipitates. In addition, they hinted that the increase in the sound velocity might be related to the Young's moduli increase due to Ni and Ti depletion.…”

The origin of the effect of aging on the thermoelectric power of maraging C250 steel

“…Currently, the identification of the aging state of maraging steel is mostly based on destructive measurements, semi-non-destructive microhardness tests and nondestructive resistivity and magnetic measurements [1,[10][11][12][13]. Another potential non-destructive method for monitoring the aging state of maraging steels is the measurement of thermoelectric power (TEP), also known as the Seeback coefficient (S).…”