STRUCTURAL CHANGES IN STEELS CAUSED BY INTERACTION WITH HIGH-TEMPERATURE COMPRESSED GAS STREAMS

Journal Article · Sat Sep 01 04:00:00 EDT 1962 · Metalloved. i Term. Obrabotka Metal.

OSTI ID:4794484

Grozin, B D; Nizhnik, S B; Yankevich, V F

In order to determine the properties of surface layers formed on steels, the interaction between the metal and high-temperature, high-pressure gases was investigated. The gas mixture was obtained from the burning of smokeless powder; its pressure reached 1300 kg/cm/sup 2/ for the duration of 0,0025 sec. A thin surface layer of the metal was heated during the rapid burning to 900 to 1000 deg C at a rate of 3 to 40O,0O0 deg C/sec. Spectrographic analysis of the surface layer revealed that C and N from the gas phase diffused into the metal to a depth of 10 microns, forming a nitrided and carbided austenitic phase. The thickness of the whitish layer was found to decrease as the annealing temperature of the steel was increased. The phase composition of the layer formed under high pressure and at high temperature was found to possess differert crystal lattice parameters and presented a different dispersion of the carbide phase than the ordinary annealed metal. (TTT) O H562 The carbide phase of hardened and annealed steel specimens containing 0.83% C was studied by electron diffraction methods. It was found that as a result of annealing at 200 deg C for 100 hours, at 300 deg C for 20 seconds, and at 400 deg C for 10 seconds the orthorhombic cementite lattice could not be observed. However, after longer soaking periods at the 2 higher temperatures for longer periods of time, in addition to the cementite, the presence of epsilon -carbide could also be established; after further increase of the soaking time and temperature, only the cementite remained in the system. The carbide had a tendency of forming layers; the crystalline precipitates in the grains were orierted in 1 or 2 directions. At 400 deg C spheroidization took place, conserving the orientation of the particles. At 500 deg C the ferrite matrix recrystallized and the orientation of the carbide particles disappeared. Upon further increase of the temperature to 600 and 700 deg C the carbide particles at the grain boundary of the ferrite continued to grow while the particles within the grains were dissolved. Annealing at 700 deg C for 20 hours resulted in the concentration of all the carbide precipitates at the grain boundaries. (TTT)

• Research Organization: Inst. of Mechanics, Academy of Sciences, Ukrainian SSR
• NSA Number: NSA-17-000561
• OSTI ID: 4794484
• Journal Information: Metalloved. i Term. Obrabotka Metal., Journal Name: Metalloved. i Term. Obrabotka Metal. Vol. Vol: No. 9
• Country of Publication: Country unknown/Code not available
• Language: Russian

Related Subjects

ANNEALING
AUSTENITE
CARBIDES
COMBUSTION
DISPERSIONS
EXPLOSIONS
GASES
HIGH TEMPERATURE
LATTICES
LAYERS
METALS, CERAMICS, AND OTHER MATERIALS
NITRIDES
POWDERS
PRESSURE
QUALITATIVE ANALYSIS
SPECTROMETERS
STEELS
SURFACES
THICKNESS
VARIATIONS