Maraging steel

About: Maraging steel is a research topic. Over the lifetime, 1728 publications have been published within this topic receiving 19886 citations. The topic is also known as: martensitic ageing steel.

Correlation between the intergranular brittleness and precipitation reactions during isothermal aging of an Fe–Ni–Mn maraging steel

Abstract: Evolution of the intergranular brittleness of an Fe–10Ni–7Mn (weight pct) maraging steel was correlated with precipitation reactions during isothermal aging at 753 K. Intergranular brittleness of the Fe–Ni–Mn steel raises after aging treatment which occurs catastrophically at zero tensile elongation in the underaged and peakaged steels. The intergranular failure is attributed to grain boundary weakening due to the formation of coarse grain boundary precipitates associated with solute-depleted precipitate-free zones during isothermal aging. Further, evidences of planar slip bands were found within the grains of a peakaged specimen loaded by tensile deformation. Those inhomogeneously deformed bands were identified to apply large strain localization in the soft precipitate-free zones at grain boundaries which is assumed to fascinate microcracks initiation at negligible macroscopic strains in the underaged and peakaged steels. During further aging, concurrent reactions including (i) overaging of matrix precipitates, (ii) spheroidization of grain boundary precipitates, (iii) growth of precipitate-free zone in width and (iv) diffusional transformation to austenite take place which increase tensile ductility after prolonged aging.

Phase chemistry and precipitation reactions in maraging steels: Part II. Co–free T–300 steel

Abstract: This article describes studies of phase transformations during aging in a commercial Co-free T-300 maraging steel. Atom-probe field-ion microscopy (APFIM) was the main research technique employed. Thermochemical calculation was used to aid the interpretation of results. The composition and morphology of precipitates were compared in the same maraging system aged at different temperatures for different times to investigate the aging sequence. Ni3Ti and Fe7Mo6 have been found to contribute to age hardening. The formation of the Fe7Mo6 phase took place at a much later stage of aging in the Co-free steel than in the equivalent Co-containing material. The matrix concentration of Mo was correspondingly higher at earlier stages of aging. No reverted austenite has been found during APFIM and transmission electron microscopy (TEM) examinations of specimens heat-treated at 510 °C, even after 360 hours of aging.

Design of laser parameters for selectively laser melted maraging steel based on deposited energy density

Abstract: In this study, the effects of laser power and scan speed on the relative density, melt pool depth, and Vickers hardness of selectively laser melted (SLM) maraging steel were systematically investigated. The change in these structural parameters and hardness could not always be clarified by the volumetric energy density, which is widely used in the SLM processes. The deposited energy density, wherein the thermal diffusion length is used as a heat-distributed depth, can express the change in these structural parameters and the hardness with one curve. To clarify the effect of the laser parameters, the deposited energy should be used instead of the volumetric energy density. Thus, this study provides a new insight on the selection of the laser condition for SLM-fabricated materials.

Thermal embrittlement of 18 Ni(350) maraging steel

Abstract: The embrittlement of as-solutionized 18 Ni(350) Maraging steel was monitored as a function of heat treatment variables by means of Charpy impact tests The processing parameters of interest were annealing temperatures in the range of 1900° to 2400°F, intermediate holding temperatures in the range of 1300° to 1800°F, and the quenching rate The changes in fracture mode with heat treatment were characterized by replica and scanning electron microscopy The severity of thermal embrittlement increases with decreasing cooling rate from the annealing treatment upon direct quenching to room temperature Intermediate isothermal holding, particularly at 1500° to 1600°F, further accentuates the embrittlement A large grain size is beneficial to the toughness when rapid direct quenches from the annealing range are imposed but is detrimental upon air cooling or intermediate holding The major loss in toughness may be associated with the diffusion of interstitial impurity atoms (C+N) to the austenite grain boundaries during cooling or intermediate isothermal holding below 2000°F An advanced stage of the embrittlement is characterized by the discrete precipitation of Ti(C,N) platelets on these boundaries Thermal embrittlement is accompanied by change in fracture mode from transgranular dimpled rupture to intergranular quasi-cleavage

A study of grain boundary segregants in thermally embrittled maraging steel

Abstract: Auger electron spectroscopy was employed to directly determine the cause of thermal embrittlement of 250 series maraging steel. A drop in CVN energy with introduction of an embrittling intermediate anneal was directly correlated with a build-up of both Ti and C on the prior austenite grain boundaries. By following grain boundary concentration of Ti as a function of time at a given temperature, the diffusion coefficient for Ti in the maraging steel at 1600°F was determined. Finally, the further drastic drop in CVN energy on aging an embrittled specimen was shown to be due to a segregation of B to the already embrittled prior austenite grain boundaries, causing a further loss of cohesion.