the amount of molybden conforming to the preceding criteria a first example in accordance with the third embodiment of the present invention comprises a composition falling within the confines of quadrilateral mcdn zone i which is subjected to hardening in blast or calm air at a temperature in the range of 1075 u00b0 c to 1125 u00b0 c if for example an alloy is selected having 2 c 27 cr 3 mo 0 4 si 0 4 mn 0 06 p and 0 06 s after hardening it will have in solid solution approximately 0 40 c 14 cr and 3 mo it is presumed that the molybdenum is distributed uniformly between the carbides and the solid solution the alloy thus is composed of primary and secondary chromium carbides and substantially a martensitic solid solution which is free of ferrite the total hardness of the example cast iron being discussed after hardening is 63 67 rc a second example in accordance with the third embodiment of the invention comprises an alloy defined by the quadrilateral kmnl zone ii which is hardened at a temperature between 1075 u00b0 and 1140 u00b0 c such an example may have 2 c 28 6 cr 2 mo 0 4 si 0 4 mn 0 06 p and 0 06 s after hardening the alloy in this example will have in solid.