Nondestructive Characterization of Thermal Ageing Behaviour at 753 K in M250 Maraging Steel (original) (raw)
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Nondestructive characterization of thermal ageing behavior at 753 K in M250 Maraging Steel
Maraging steel M250 is widely used in aerospace industry for fabrication of critical rocket motor casings. Specific heat-treatment is given to these parts before they are put into service. Qualification of the heat treatments is presently based on the microscrostructural examination carried out on test coupons, which is indirect tedious, destructive in nature and only limited sampling based. For the complete, faster, accurate and insitu qualification of the actual heat treatment given to the actual component, non-destructive inspection techniques based methodology has been developed. Two NDE techniques, magnetic Barkhausen emission (MBE) and ultrasonic techniques have been used for the characterization of thermal ageing behaviour of the steel at 753 K. The MBE technique has been chosen due to the ferromagnetic nature of the maraging steel. While the MBE technique provides the near surface information, the ultrasonic technique characterizes the bulk of the component. The present study has clearly brought out the complementary nature of these two techniques for the characterization of thermal ageing behaviour in M250 maraging steel. Ultrasonic measurements have been found to be more sensitive to the precipitation of intermetallics, whereas, MBE could clearly identify the onset of austenitic reversion.
2016
Microstructural changes during thermal ageing of ferromagnetic mater ials can be detected in a rapid and nondestructive way by means of micromag netic methods. The Fraunhofer Institute for Nondestructive Testing (IZFP) proves the suitability of those techniques for the characterization of microstructural ch anges caused by thermal ageing (at different times and temperatures) of the d i fer nt heat resistant ferritic, ferritic/martensitic steels and iron-based alloys. Differing microstructure features and subsequent thermal ageing of high chromium ferritic steels produces populations of strengthening Laves phase precipitates, largely deviating from each other in terms of particle number, size distribution and inter-particle spacing and thus differing mechanical prop erties. The effect of different thermal ageing procedures on the microstructure evolution was characterized by means of micromagnetic techniques. Thermal aged and creep damaged 9-12Cr ferritic/martensitic steel specimens ...
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007
Nondestructive measurements have been carried out in M250 grade maraging steel specimens subjected to solution annealing at 1093 K for 1 h followed by ageing at 755 K for various durations in the range of 0.25 to 100 h. Different NDE techniques such as ultrasonic velocity, magnetic barkhausen emission (MBE), positron annihilation spectroscopy (PAS), eddy current and X-ray diffraction (XRD) have been employed for comprehensive characterization of microstructural features evolved consequent to aging treatment.
Ultrasonic Characterization of Aging Behavior in M250 Grade Maraging Steel
Metallurgical and Materials Transactions A, 2009
The increase in sound velocities during the aging of M250 maraging steel reported by Rajkumar et al. was analyzed. The present article provides a new perspective on why and to what extent the sound velocities change during aging. The main parameter that affects the elastic moduli and the sound velocities in the early and intermediate stages of aging in maraging steel is the depletion of Ni from the martensitic matrix due to Ni 3 Ti and Ni 3 Mo formation. The issue of sound velocity increase with aging time was addressed here in a few different ways to support the validity of Ni depletion.
NDT & E International, 2004
Low alloy steel such as 1.25Cr-0.50 Mo steel is widely used in thermal power plants, petrochemical industries and fertiliser plants. In recent years considerable attention has been paid to estimate the remaining life of a service-exposed component for effective utilising such components beyond the design life. Although these steels are heat treated to obtain a stable microstructure, microstructural changes such as carbide coarsening, increasing inter lamella spacing, formation of more stable carbides, dissolution of carbides, etc. take place due to prolong service exposure at elevated temperatures. This paper describes the systematic investigation on microstructural changes, changes of composition on carbides and their effect on the magnetic Barkhausen emission parameters. The materials were heat-treated at different temperatures (500-700 8C) for various duration of time (0-1000 h) to get wide variation in microstructure. RMS voltage and pulse height distributions of Barkhausen emissions signal were calculated. A good correlation between MBE parameters and microstructural changes has been found. The study will be useful for the non-destructive evaluation of microstructural degradation of in-service 1.25Cr-0.5Mo steel structure.
Maraging steels gain many of their beneficial properties from heat treatments which induce the precipitation of intermetallic compounds. We consider here a two-stage heat-treatment, first involving austenitisation, followed by quenching to produce martensite and then an ageing treatment at a lower temperature to precipitation harden the martensite of a maraging steel. It is shown that with a suitable choice of the initial austenitisation temperature, the steel can be heat treated to produce enhanced toughness, strength and creep resistance. A combination of small angle neutron scattering, scanning electron microscopy, electron back-scattered diffraction, and atom probe tomography were used to relate the microstructural changes to mechanical properties. It is shown that such a combination of characterisation methods is necessary to quantify this complex alloy, and relate these microstructural changes to mechanical properties. It is concluded that a higher austenitisation temperature leads to a greater volume fraction of smaller Laves phase precipitates formed during ageing, which increase the strength and creep resistance but reduces toughness.
Metallurgical and Materials Transactions A, 2008
X-ray diffraction (XRD) studies were carried out to characterize aging behavior of M250 grade maraging steel samples subjected to isothermal aging at 755 K for varying durations of 0.25, 1, 3, 10, 40, 70, and 100 hours. Earlier studies had shown typical features of precipitation hardening, wherein the hardness increased to a peak value due to precipitation of intermetallics and decreased upon further aging (overaging) due to reversion of martensite to austenite. Intermetallic precipitates, while coherent, are expected to increase the microstrain in the matrix. Hence, an attempt has been made in the present study to understand the microstructural changes in these samples using XRD line profile analysis. The anisotropic broadening with diffraction angle observed in the simple Williamson-Hall (WH) plot has been addressed using the modified WH (mWH) approach, which takes into account the contrast caused by dislocations on line profiles, leading to new scaling factors in the WH plot. The normalized mean square strain and crystallite size estimated from mWH have been used to infer early precipitation and to characterize aging behavior. The normalized mean square strain has been used to determine the Avrami exponent in the Johnson-Mehl-Avrami (JMA) equation, which deals with the kinetics of precipitation. The Avrami exponent thus determined has matched well with values found by other methods, as reported in literature.
INFLUENCE OF AGING TEMPERATURE ON MECHANICAL PROPERTIES AND SOUND VELOCITY IN MARAGING STEEL M350
2010
ABSTRACT In the present work, the influence of aging temperature on mechanical properties and sound velocity of Maraging steel M350 was investigated. For this purpose, first, samples were solution annealed at 825 • C for 2 hours and then age hardened at 510 • C-600 • C for 3 hours. Hardness, tensile and impact tests were used for determining mechanical properties and longitudinal ultrasonic velocity was used for determining sound velocity of the samples. The obtained results indicated that hardness, strength and sound velocity of the samples decreases with increase of ageing temperature, whereas, toughness of the samples increases directly with ageing temperature. These results were attributed to the dissolution of Ni 3 (Mo,Ti) and Fe 2 Mo precipitates and also to the formation of reverted austenite which are promoted by the increase of ageing temperature. Optical microscopy of the samples revealed that, in this case, the morphology of reverted austenite is mainly of grain boundary and interlath type. Further, a linear correlation between the mechanical properties and sound velocity of the samples was found that can be used in industrial applications.
Nondestructive Testing and Evaluation, 2023
The service life and structural safety of components are affected by the thermal ageing of materials; therefore, a non-destructive evaluation of materials is extremely essential and crucial. In this work, heat-resistant steel Cr12MoV was selected as a specimen, and the embrittlement period of heat-resistant steel Cr12MoV was obtained by accelerated thermal ageing experiments. The effects of service temperature and service time on the mechanical properties of heatresistant steel were analysed. The non-destructive testing of heatresistant steel was carried out by using magneto-acoustic compound detection techniques based on electromagnetic acoustic transducers. In the process, magneto-acoustic compound detection signals were decoupled. The electromagnetic characteristic parameters and ultrasonic characteristic parameters of the detection signals were extracted to evaluate the mechanical properties and thermal ageing of heat-resistant steel. The quantitative evaluation ability of thermal ageing brittleness of heat-resistant steel was improved by using the magneto-acoustic compound detection techniques compared with single eddy current detection method or single ultrasonic detection method.