LAUSR

In the present work, paraffin phase change material is used as quenchant for the heat treatment of 42CrMo4 alloy and compared with water, air, and CuO doped paraffin. The samples were prepared based on ASTM E 8M-98 standard for tensile test and then heated up to 830 °C, kept for 4 h in an electric resistance furnace and then quenched in the mentioned media. Elastic modulus, yield strength, ultimate tensile strength, elongation, and modulus of toughness were determined according to the obtained stress-strain curves. Moreover, the hardness and microstructural evolution were investigated after the heat treatment at different media. The samples quenched in paraffin and CuO-doped paraffin are higher in ultimate tensile strength (1439 and 1306 MPa, respectively) than those quenched in water (1190 MPa) and air (1010 MPa). The highest hardness, with a value of HV 552, belonged to the sample quenched in CuO-doped paraffin. The microstructural studies revealed that the non-tempered steel had a ferrite/pearlite microstructure, while by quenching in water, paraffin and CuO-doped paraffin, ferrite/martensite microstructures were achieved. It is also observed that using the air as quenchant resulted in a three-phase bainite/martensite/ferrite microstructure. 采用石蜡相变材料作为42CrMo4 合金热处理的淬火介质, 并与用水、空气和CuO 掺杂石蜡作 淬火介质进行比较。根据ASTME8M−98 标准制备拉伸试样, 将试样在电阻炉中加热至830 °C, 然后 保温4 h, 再在上述介质中淬火。根据得到的应力−应变曲线确定弹性模量、屈服强度、极限抗拉强度、 伸长率和韧性模量。此外, 还研究了不同介质热处理后的硬度和显微组织演化。石蜡与CuO 掺杂石 蜡淬火样品的极限抗拉强度(分别为1439 和1306 MPa)高于在水(1190 MPa)和空气(1010 MPa)中淬火样 品的。CuO 掺杂石蜡淬火样品的硬度最高, 为HV552。显微组织研究表明, 非淬火钢具有铁素体/珠 光体组织, 而在水、石蜡和CuO 掺杂石蜡中淬火, 可获得铁素体/马氏体组织; 还观察到, 以空气为 淬火介质, 形成贝氏体/马氏体/铁素体三相组织。