铬和钼对精铸热锻模具钢高温磨损行为的影响

采用销盘式高温磨损试验机,研究不同Cr、Mo含量的精铸热锻模具钢的高温磨损行为;通过TEM、SEM和XRD分析,研究钢的显微组织和磨损表面的形貌和结构;探讨了成分、组织、性能与高温磨损的关系及高温磨损机理。结果表明,随着Cr、Mo分别从3%和2%增加到5%和4%,热稳定性和硬度分别得到明显降低或略提高,当含4.0%Cr和3.0%Mo时,耐磨性最好。高温磨损抗力对钢的热稳定性和热强性变化不敏感,而对钢的组织或韧性变化极敏感。过高的铬（5%）虽降低热稳定性和热强性,但仍具有较高的高温耐磨性;而过高的钼（4%）虽然热稳定性和热强性提高,由于Mo6C沿晶界或板条界析出,韧性降低,则高温耐磨性明显降低。精铸热锻模具钢高温磨损机理为氧化磨损和氧化物的疲劳剥落,磨面上产生的氧化物主要为Fe3O4和Fe2O3,其对磨损起到保护作用,氧化物的疲劳剥落导致磨损。

Effect of Cr and Mo on High-Temperature Wear Behavior of Cast Hot-Forging Die Steels

The high temperature wear behavior of cast hot-forging die steels with different contents of Cr and Mo was studied using a pin-on-desk high-temperature wear tester. The microstructure, worn morphology and microstructure of cast hot-forging die steels were analyzed with TEM,SEM and XRD. The mechanism and relation of high temperature wear with composition, microstructure and properties were discussed. The results show that thermal stability and hardness of the cast steels are significantly decreased and slightly increased with increasing contents of Cr and Mo from 3wt% and 2wt% to 5wt% and 4wt%respectively. The cast steel with 4wt%Cr and 3wt%Mo has the best wear resistance. It is found that high temperature wear resistance is not sensitive to thermal strength and stability, however it is very sensitive to microstructure and toughness. Although the very high Cr content (5wt%) decreases thermal strength and stability, but the steel still has higher wear resistance. On the other hand, although the very high Mo content(4wt%) increases thermal strength and stability, the toughness decreases due to Mo6C precipitation along boundaries of marternsite laths and grains, thus the high temperature wear resistance decreases obviously. The wear mechanism is oxidation wear to protect from wear, and oxide fatigue delamination to cause wear with predominant oxides of Fe3O4 and Fe2O3 on worn track.