淬火温度对添加B_4C的ASP30粉末冶金高速钢组织及力学性能的影响

采用粉末冶金方法制备添加B_4C的全致密ASP30高速钢,样品在1 040℃到1 200℃范围内淬火,并且经过560℃三次回火,研究淬火温度对其力学性能及显微组织的影响。采用扫描电子显微镜、洛氏硬度计和材料力学性能测试机研究高速钢的组织和力学性能。结果表明:添加质量分数为0.025%B_4C的ASP30粉末冶金高速钢在1 160℃下烧结2 h后会形成月牙形液相碳化物,从而获得全致密的烧结组织。随淬火温度升高,显微组织中碳化物的数量明显减少,基体中合金元素固溶含量提高,基体晶粒长大,断口形貌呈准解理断裂但断口平整度下降。随淬火温度升高,钢的硬度提高,最高值达到69 HRC。抗弯强度、断裂韧性均下降,抗弯强度最高值达4 357MPa,断裂韧性最高值为48.6 MPa/m1/2。冲击韧性先升高后下降,在1 080℃最高为18.85 J/cm2。

Effect of quenching temperature on microstructures and mechanical properties of ASP30 added B4C powder metallurgy high speed steel

In this work, fully dense ASP30 high speed steel (HSS) with B4C addition was prepared by powder metallurgy technology. The samples were quenched at temperatures from 1 040 ℃ to 1 200 ℃, and then tempered three times at 560℃. The effect of different quenching temperatures on mechanical properties and microstructures was investigated. Scanning electron microscope, rockwell apparatus and mechanical property tests were used to study the microstructure and mechanical properties of the HSS. The results show that ASP30 HSS containing 0.025% B4C is fully dense after sintered at 1160 ℃ for 2 h, because of the formation of liquid phase. With increasing quenching temperature, the carbides content increases, the alloying element content in the matrix and the grain size of the matrix increase. In addition, the fracture surface is quasi-cleavage fracture, but the flatness decrease. Meanwhile, the hardness of HSS increases gradually with increasing quenching temperature. The maximum hardness of 69 HRC is obtained at 1 200℃. Moreover, both bending strength and fracture toughness decrease,with the highest values of 4 357 MPa and 48.6 MPa/m1/2, respectively. The highest impact toughness of 18.85 J/cm2 is obtained at 1 080℃.