Optimización del tratamiento térmico en aceros maraging fabricados sin cobalto y sin molibdeno mediante “selective laser melting” (SLM)

Abstract

Maraging steels are martensitic steels without C. Their main alloy elements are Ni, Co, Mo, Ti and Al. These steels undergo solution treatments and subsequent ageing at temperatures in the range of 450ºC to 600ºC. The ageing reactions cause a strong hardening attributed to the precipitation of Ni3(Ti, Mo) and Fe2Mo. The presence of retained austenite and Laves phases is unfavourable for tensile strength. The formation of reverse austenite is due to the enrichment of austenite stabilising elements. The Selective Laser Melting (SLM) process can be characterised in terms of energy density and an important defect that can impair the interlayer bonding, affecting its fracture, which is “balling”. In this work, the ageing kinetics of a maraging steel, manufactured by SLM, without Co, without Mo and reduced Ni content, is analysed. For this purpose, the material undergoes different ageing temperatures, between 460 and 580 ºC, and different holding times. Hardness, tensile and charpy tests were carried out and the fracture facies were analysed. Faults were detected in the process parameters that caused bonding defects in the specimens.