Influence of Aging Temperature on Mechanical Properties and Sound Velocity in Maraging Steel M350

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 Ni3(Mo,Ti) and Fe2Mo 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.