The dependence of mechanical properties of maraging steels on the temperature of tempering is of the same pattern as that for all precipitation-hardenable alloys, i.e. the strength properties increase to a maximum, after which softening takes place. By analogy with ageing, the stages of hardening and softening tempering may be separated in the process.

The hardening effect is caused by the formation of segregates at dislocations and, what is most important, by the formation of partially coherent precipitates of intermediate phases of the type Ni3Ti or Ni3Mo. The softening is due, in the first place, to replacement of disperse precipitates having greater interparticle spacing and, in the second place, to the reverse ������ martensitic transformation which is accompanied by the dissolution of intermetallics in the austenite.

The ultimate strength of maraging steels increases on tempering roughly by 80% and the yield limit, by 140%, i.e. the relative gain in strength properties is not greater than in typical age-hardening alloys, such as beryllium bronze or aluminum alloy Grade 1915, but the absolute values of ultimate and yield strength on tempering of maraging steels reach record figures among all precipitation hardening alloys. This is mainly due to the fact that maraging steels have a very high strength (Rm = 1100 MPa) in the initial (as-hardened) state.

The high strength of maraging steels on tempering at 480-500��C for 1-3 hours may be explained by the precipitation of very disperse semi coherent particles of the size and interparticle spacing of an order of 103 nm in the strong matrix, these intermetallic precipitates also possessing a high strength. Thus, with the same dispersity of precipitates as that of G. P. zones in precipitation, hardening non-ferrous alloys, maraging steels possess an appreciably higher ultimate strength (Rm = 1800-2000 MPa).

As compared with martensite-hardenable carbon-containing steels, carbonless maraging steels show, for the same strength, a substantially greater resistance to brittle fracture, which is their most remarkable merit. On tempering to the maximum strength, the ductility indices and impact toughness, though diminish somewhat, still remain rather high. The high ductility of the carbonless matrix and the high dispersity of uniformly distributed intermetallic precipitates are responsible for a very high resistance to cracking, which is the most valuable property of modern high-strength structural materials.

The properties of maraging steels clearly indicate that these steels have many potential applications in mechanical components of electro-mechanical data processing machines. Use of these steels in shafts that require good dimensional control following heat treatment should be pursued for two reasons. First, maintaining dimensions should be easier because quenching and tempering are not necessary. Second, wear data indicate that equivalent or better wear resistance is obtained from the maraging steel than from the more commonly used shaft materials.

Impact-fatigue strength of 18% Ni-maraging steels indicates that these steels could be used in repeated impact loading situations. The good fracture toughness, compared to that of quenched and tempered alloy steels at the same strength level, indicates possible use in high-impact low-cycle load applications.

Finally, due to the relatively low temperature of aging, the use of the maraging steels for long, thin parts should be considered. Here, their use as a replacement for some case hardened or nitrided components is indicated that the potential application should be carefully studied.