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对3.55C-1.95Si-0.36Mn-3.58Ni-0.708Cu-0.92Mo-0.65Cr(质量分数,%)低合金贝氏体球墨铸铁实施等温淬火及不同温度的回火热处理工艺,采用OM,EPMA,SEM,TEM以及XRD研究了回火温度对等温淬火低合金贝氏体球墨铸铁的组织演变过程的影响,并对力学性能和耐磨性进行了测试与分析.结果表明,回火过程组织演变的物理机制包括孪晶马氏体及其位错亚结构的回复与再结晶软化、残余奥氏体分解、马氏体中过饱和碳的脱溶与相变以及共晶渗碳体的转变等过程.随着回火温度的升高,等温淬火低合金贝氏体球墨铸铁基体的显微硬度和宏观硬度及抗压强度逐渐降低.在450℃回火后,共晶渗碳体的显微硬度出现最低值,其原因是,在此温度下共晶渗碳体的亚片层有a相析出,此时,低合金贝氏体球墨铸铁的压缩率最高,塑性提高;在600℃回火时,其力学性能明显恶化.在干砂/橡胶轮磨损条件下,450℃回火后的等温淬火低合金贝氏体球墨铸铁具有较好的耐磨性.磨损形貌观察表明,其磨损机制为塑性变形疲劳磨损和显微切削,塑性变形疲劳机制对耐磨性的贡献大于切削破坏机制,在450℃回火析出的弥散Mo2C对耐磨性也有一定贡献.
The austenitizing and tempering heat treatment of 3.55C-1.95Si-0.36Mn-3.58Ni-0.708Cu-0.92Mo-0.65Cr (mass fraction,%) low alloy bainite ductile iron was carried out by OM, EPMA SEM, TEM and XRD were used to investigate the effect of tempering temperature on the microstructure evolution of austempered low-bainitic nodular cast iron. The mechanical properties and wear resistance were also tested and analyzed. The results show that the microstructure evolution during tempering The physical mechanisms include the recovery and recrystallization softening of twinned martensite and its dislocation sub-structure, the residual austenite decomposition, the desolventizing and transformation of supersaturated carbon in martensite and the transformation of eutectic cementite With the increase of tempering temperature, the microhardness, macrohardness and compressive strength of the isothermal quenched low-alloy bainitic ductile iron matrix gradually decrease.After tempering at 450 ℃, the microstructure of eutectic cementite The reason for the lowest hardness appears at this temperature is the eutectic cementite sublayer has a phase precipitation, this time, the low alloy bainite ductile iron compression rate, plastic increased; at 600 ℃ tempering , Its mechanical properties significantly deteriorated in the dry sand / rubber wheel wear conditions, 450 ℃ tempering Of austempered low-alloy bainite ductile iron has better wear resistance.The observation of wear morphology shows that the wear mechanism is plastic deformation fatigue wear and micro-cutting, and the plastic deformation fatigue mechanism contributes more to wear resistance than cutting failure Mechanism, at 450 ℃ tempering precipitation of Mo2C dispersion also has a certain contribution to wear resistance.