Actually the very high strength Maraging steels are not necessarily tough. Their high tensile strength can come at the cost of low fracture toughness, also known as critical stress intensity factor. Brittle fracture can then occur due to small initial flaws, cracks for example, at relatively low stress levels.
The tradeoff between fracture toughness and tensile strength is part of the design selection process for steel, as typically higher values for one are associated with lower values for the others.
Pressure vessel design text books sometimes use failures of Maraging steel pressure vessels as examples of the results of steel selection focusing on tensile strength, while neglecting fracture toughness required due to possible initial flaws.
When you start getting into the intricate details of design all sorts of possible problems must be addressed with any material. Surface flaws and/or cracks are potential issues with just about any material. I suppose someone could utilize Maraging steel for a pressure vessel to reduce weight or something, but considering the potential results I doubt that idea would get past an initial process safety review with us.
I have found the maraging steels - not the very high tensile stuff, the 300+ kpsi stuff - to be both strong and pretty tough. Metallurgists sometimes don't know it all either. We had a round hollow piston that was hammering bagasse basically, and we were wearing them out wholesale. Talking with the equipment vendor, we decided to try making one out of hardened D2 tool steel. The metallurgists recommended against it because the tensile values are so erratic, but we were mainly concerned with compression and toughness, and even at the low end the tensile was more than adequate. The D2 outlasted everything else by 5 to one.
