| The effect of tempering on the growth behavior of M₂C precipitates was examined. Applied tempering temperatures were 468, 482 and 510℃, and tempering time varied from 1 to 400 hours. The value of peak hardness was HRc 55 in all temperatures and the shift of peak hardness to earlier tempering time occurred with an increase in temperature. The peak hardness was obtained, when the average length and diameter of M₂C carbides were 4∼8 ㎚ and 1.5∼2.5 ㎚, respectively. The size of M₂C carbides increased with tempering time, and the size of carbides at 510℃ was larger than that at 482 or 468℃ in all tempering time. The aspect ratio of M₂C carbides was almost 3 in all tempering conditions. The amount of precipitated austenites increased with tempering time and temperatures. Experimental studies of grow th behavior of the carbides in this steel have been made by using TEM, SEM and X-ray diffraction. |
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