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 1390.    HEIDENREICH, R. D., STURKEY, L., AND WOODS, H. L.  Decomposition of Martensitic Steel Above and Below 300°.  Nature, vol. 157, 1946, p. 518; Chem. Abs., vol. 40, 1946, p. 5382.

        Electron microscope and electron-diffraction methods were used to study metallurgical structures in a plan C steel, 0.9%, 0.15% Si, 0.0056% N.  Martensite aged at 200° gives a fine dispersion of hexagonal Fe₃N but no Fe₃C.  Above 300° the reaction product is Fe₃C.  A specimen aged at 200° shows both Fe₃N and Fe₃C after 30 min. at 350°.  A mechanism is suggested:  (1)  Fe+C_solution, +N_solution, martensite, ^200°→Fe₃N or Fe₃(CN)+C_solution; (2) Fe+C_solution, martensite, ^400°→Fe₃C+N_solution; (3) Fe₃N or Fe₃CN+C_solution^350°→Fe₃C+N_solution.  The preparation of satisfactory surfaces involved (1) abrasion through 3/0 metallographic paper; (2) electrolytic polishing; (3) etching 60-90 sec. in 2% Hcl and 1% FeCl₃ in MeOH; (4) rinsing (a) 50:50 Me₂CO-MeOH+0.5% HCOOH, (b) 50:50 Me₂ CO-MeOH, (c) dry C₆H₆; (5) drying in an air blast.

       HEIN, L. B.  See abs. 701a.