Metal Science and Heat Treatment

doi: 10.1007/BF00648711pmid: N/A

Gulyaev, A.; Karchevskaya, N.

doi: 10.1007/BF00648712pmid: N/A

1. Molybdenum decreases the temperature interval in which martensite is formed in Fe+20% Ni alloys, while cobalt increases it. The additional elements investigated here affect the temperature interval of the martensitic transformation in the same way as that in steel. 2. Since the alloys must have a martensitic structure before aging (the effect of aging is due to the processes occurring in the α-phase), the amount of molybdenum—which sharply decreases the temperature of the martensitic points—should be limited to 3% (if the alloys are not subjected to cold temperatures). In the presence of cobalt—an element increasing the temperature of the martensite points—the amount of molybdenum can be increased to 5%. The positive role of cobalt in alloys of this type is probably due to the fact that the addition of cobalt makes it possible to increase the amount of molybdenum. 3. The hardness of annealed (unaged) alloys is independent of the ratio between austenite and martensite. Apparently, the hardness of carbon-free and unaged martensite is practically the same as that of the initial austenite. 4. The hardness of the alloys investigated cannot be used as a criterion of their degree of quenching.

Perkas, M.

doi: 10.1007/BF00648713pmid: N/A

Litvinenko, D.; Stavitskii, Yu.

doi: 10.1007/BF00648714pmid: N/A

1. Nickel steels (9–20% Ni) containing Al, Ti, or Mo together with Co are susceptible to aging and considerable hardening during a short period of tempering at 400–550°C (maximum hardening occurs at about 500°C). 2. The hardening of steels containing 9% Ni is accompanied by a drop of plasticity and ductility. In high-nickel steels (18–20% Ni) the plasticity and ductility do not decrease so much: δ=10–12%; ψ=∼60%; ak=5.0–6.0 kgm/cm2 after a strength of δb=150–170 kg/mm2 is reached, depending on the combination of the alloyed elements. 3. Sulfur and phosphorus sharply decrease the plasticity and ductility and the impact strength of steels containing 18–20% Ni with martensite which can be aged, and therefore the amounts of these impurities should be strictly limited to less than 0.010% of each. 4. High-nickel steels of both types with martensite which can be aged are characterized by a high resistance to brittle fracture; these steels are not susceptible to brittleness due to tempering, and are very little sensitive to cuts; they are hardenable in air to a depth of 200 mm. 5. Hardened steels with martensite which can be aged have a high fatigue resistance in both smooth and notched samples (70–72 and 28–30 kg/mm2 respectively).

Kardonskii, V.; Perkas, M.

doi: 10.1007/BF00648715pmid: N/A

1. Aging with precipitation of (Ni, Fe) Al and Ni3Al occurs in the α-phase which has a martensitic structure and in the ferrite which has a structure close to the equilibrium structure. The state of the initial α-phase has an effect on hardening resulting from aging. 2. Hardening resulting from aging at 350–450°C is not accompanied by any visible change in the structure of the alloy. Only after aging at 500°C can one see areas (less than 20A in size) with an ordered (Ni, Fe) Al structure. This result leads us to conclude that these areas are also formed at lower temperature, but their size and number are probably much smaller. At temperatures above 500°C not only areas of the (Ni, Fe) Al phase are formed, but also large precipitates of Ni3Al. These precipitates do not play any significant role in the hardening of the α-phase resulting from aging. 3. The increase in hardness as the result of aging is due to the initial stage of the formation of areas with (Ni, Fe) Al structure which are coherent with the matrix. It is probable that it is the ordering of the structure which is responsible for the hardening of the alloy resulting from aging.

Spiridonov, V.; Skakov, Yu.; Iordanskii, V.

doi: 10.1007/BF00648716pmid: N/A

1) The changes in the properties of Cr\t-Ni steels with a martensitic structure alloyed with Al, Cu, Al+Mo, or Cu+Mo which result from aging occur in two stages. Aging is limited by diffusion at all stages. During the initial stage the determining factor is the \lddrift\rd of dissolved atoms toward dislocations under the effect of the stressfield, while during the second stage the determining factor is normal diffusion due to the chemical gradient. In steels containing Mo the second stage of aging is very weakly expressed. 2) Hardening induced by aging is apparently due to the initial stage of decompostion, when the dislocations become pinned. The aging of steels containing Cu or Al is due to the formation of precipitates which can be made evident by microscopic and electronographic analysis. 2) The concentration and the character of structural defects affect the kinetics of hardening and softening during aging. Martensite formed as the result of treatment at very low temperature and possessing a large number of crystals with internal twins softens the least rapidly.

Spektor, Ya.; Voronina, S.

doi: 10.1007/BF00648717pmid: N/A

doi: 10.1007/BF00648718pmid: N/A

doi: 10.1007/BF00648719pmid: N/A

Gol'denberg, A.; Doronin, V.; P'yankova, I.

doi: 10.1007/BF00648720pmid: N/A

1. The optimum quenching temperature for 1Kh12N2VMF steel is 1000–1050°C. 2. The best combination of the strength and ductility in 1Kh12N2VMF steel (δb=110 kg/mm2) and ak=10–12 kgm/cm2) results from quenching+tempering at 570–580°C.