The Effect of Heat-Treatment on the Microstructures and Mechanical Properties of Ultrahigh-Strength Ni-Cr-Mo Steel.
Date Issued
2005
Date
2005
Author(s)
Wu, Jien-Ting
DOI
zh-TW
Abstract
The purpose of the this work is to determine the best heat-treatment condition (including the austenitizing temperature, quenching rate, subzero treatment and tempering temperature ) the four wear-resistance steels (Fe-xNi-1.5%Cr-0.5%Mo,x equals 3、5 and 7% , and Fe-5Ni%-1.0%Cr-0.5%Mo). The correlation between microstructure and mechanical properties will be discussed by optical microscope (OM), transmission electron microscope (TEM) and scanning electron microscope (SEM).
The experiment finds that the toughness and hardness are seriously influenced by the distribution and morphology of the carbide precipitates in the tempered structure.
The results show that the Ni-Cr-Mo steels can obtain high hardness and maintain good toughness by the way of oil-quenched from 850℃, subzero-treated in liquid nitrogen for 10 minutes and tempered at 150~175℃. On the contrary , tempered martensite embrittlement (TME) occurred at 250~500℃ because of retained austenite at the martensite lath boundary transformed to cementite.
Finally we want to figure out the quantity of the retained austenite in this experiment but the content of retained austenite is too little to determine by X-ray diffractometer(XRD) . So that the retained austenite was analyzed by magnetometry. The results show that the retained austenite will be stabilized when the delay-time of subzero-treatment is increased. However the more the addition of nickel in the alloy,the more increase the amount of retained austenite.
The experiment finds that the toughness and hardness are seriously influenced by the distribution and morphology of the carbide precipitates in the tempered structure.
The results show that the Ni-Cr-Mo steels can obtain high hardness and maintain good toughness by the way of oil-quenched from 850℃, subzero-treated in liquid nitrogen for 10 minutes and tempered at 150~175℃. On the contrary , tempered martensite embrittlement (TME) occurred at 250~500℃ because of retained austenite at the martensite lath boundary transformed to cementite.
Finally we want to figure out the quantity of the retained austenite in this experiment but the content of retained austenite is too little to determine by X-ray diffractometer(XRD) . So that the retained austenite was analyzed by magnetometry. The results show that the retained austenite will be stabilized when the delay-time of subzero-treatment is increased. However the more the addition of nickel in the alloy,the more increase the amount of retained austenite.
Subjects
深冷處理
回火麻田散鐵脆性
殘留沃斯田鐵
Subzero treatment
tempered martensite embrittlement
retained austenite
Type
thesis
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