Maraging Steel
Maraging steels are very strong and have ultra-low carbon contents (0.03%) and sometimes contain no carbon at all. They get their strength from intermetallic compounds rather than carbon. The main alloying element is 15% to 25% nickel. Other alloying elements added to produce intermetallic precipitates include cobalt, molybdenum, and titanium. Original development was carried out on 20% and 25% Ni steels to which small additions of Al, Ti, and Nb were made.[1] Given the expected high cost of carbon on the Moon largely due to the fact that robots will have to mine millions of tons of regolith every year to produce tens of tons of carbon and life support systems will get "first dibs" on carbon supplies, carbonless maraging steels are worth considering. Nickel and cobalt are present in meteoric iron fines found all over the Moon. These particles contain from 5% to 10% nickel and about 0.2% cobalt. Since the meteoric fines are present at about 0.5% a robot mining a square kilometer to a depth of 10cm could produce 1000 tons of fines and 50 to 100 tons of nickel. That would be enough nickel to make 250 to 500 tons of 20% Ni maraging steel or 200 to 400 tons of 25% Ni steel. This could be alloyed with Al and/or Ti but Nb and Mo are too rare on the Moon and Co, though it can be extracted from meteoric fines is not very pleniful.
More research needs to be done on carbonless maraging steels using only lunar available elements like nickel, aluminum and titanium. Cost comparisons must be made for carbon-steel and maraging steel and that will probably require actual experience on the Moon. We know that volatiles mining for carbon will be time consuming and energy intensive. Producing nickel will reqire mining large areas of regolith too, but low intensity magnetic separators probably won't demand as much energy as roasting solar wind implanted volatiles will. Nickel can be extracted from the fines with CO gas and poassibly by electrostatic methods. There is also the possibility of obtaining carbon from polar ices. Presently, there is no way to predict how productive or unproductive polar ice mining will be.
