329.    BRAMLEY, A., AND TURNER, G.  Gaseous Cementation of Iron and Steel.  IV.  Action of Mixtures of Carbon Monoxide and Ammonia on Iron and Steel and Its Bearing on the Process of Cementation.  Iron and Steel Inst. Carnegie Schol. Mem., vol. 17, 1928, pp. 23-66; Chem. Abs., vol. 22, 1928, p. 4437. 

                  Cementations of Armco Fe were made at various temperatures with mixtures of CO and NH₃ and with mixtures of CO and H₂.  The cementations were conducted at various temperatures ranging 700°-1,050° at intervals of 50°, and the process was continued in each case for 10 hr.  The test results prove that the carbonizing action of mixtures of CO and NH₃ is much greater than that of CO alone.  The carburizing properties of mixtures of CO and H₂ were stronger than CO alone but not so intense as corresponding mixtures containing NH₃.  Micrographs show that the microstructure of the Fe-C alloys is entirely altered by the presence of N; this is the case especially when the cementations are made at temperatures below 800°; above 800° very marked segregation of cementite takes place. 

     BRAMLEY, A., AND LAWTON, G.  Gaseous Cementation of Iron and Steel. III.  Influence of Hydrocarbons on the Carburization of Iron and Steel.  See abs. 328.