β凝固γ-TiAl和40CrMo钢的干摩擦学性能对比研究

Comparison on Dry Sliding Tribological Behavior of β-solidifying γ-TiAl alloy and 40CrMo steel

摘要:

β凝固γ-TiAl合金虽具有比传统γ-TiAl更高的强度指标和服役温度,但是目前关于这类合金的摩擦学性能和磨损机理仍缺乏系统深入的认识。本文以40CrMo钢为参照,研究了β凝固的Ti-44Al-3Mn-0.4Mo-0.4W(原子比,简称TMMW)合金在不同载荷下的干摩擦学行为。结果表明：TMMW和40CrMo钢的摩擦系数数值差异明显,且随着载荷变化呈现出不同规律；TMMW合金摩擦系数表现为先增加后保持相对稳定,而40CrMo钢的摩擦系数随着载荷的增加持续上升；随着载荷由2 N增加至10 N,TMMW合金比40CrMo钢具有更强的抗磨性,载荷为10 N时磨损率由6.97×10-3 mm3/(N·m)降低至1.88×10-4 mm3/(N·m)。TMMW合金的磨损机制以磨粒磨损为主,并伴随一些黏着磨损、磨粒磨损引起的塑性变形,而40CrMo钢以黏着磨损为主,伴随一定的氧化磨损和磨粒磨损。TMMW合金中相的硬度大小顺序为：βo＞α2＞γ,在室温干摩擦条下,βo相的耐磨性应较α2、γ相更佳。高载荷下(5~10 N),摩擦升温后,合金中存在的βo相自身软化,使得合金在对磨时容易发生塑性变形,进而确保摩擦系数数值保持相对稳定。

Abstract:

The β-solidifying γ-TiAl alloys have higher strength and service temperatures than that of conventional γ-TiAl alloys, but currently there is still a lack of systematic and in-depth understanding of the tribological properties and wear mechanisms of this type of alloy. In this study, the dry-sliding tribological behavior of a β-solidifying γ-TiAl alloy with the chemical composition of Ti-44Al-3Mn-0.4Mo-0.4W(at.%, named as TMMW) was investigated. For comparative purposes, the tribological behavior of a common 40CrMo steel was also examined under the same conditions. It was found that there is a significant difference in the friction coefficient values between TMMW and 40CrMo, and they exhibit different patterns as the load changes. The friction coefficient of TMMW alloy first increases and then remains relatively stable, while that of 42CrMo steel increases continuously with the raise of load. The wear resistance of the TMMW alloy is superior to that of the 40CrMo steel as the load increases from 2N to 10N, and the wear rate decreases from 6.97×10-3 mm3/(N·m) to 1.88×10-4 mm3/(N·m) under the 10N load. The wear mechanisms of TMMW alloy are mainly abrasive wear, accompanied by some adhesive wear and plastic deformation caused by abrasive wear, while that of 40CrMo steel is mainly adhesive wear, accompanied by certain abrasive wear and oxidation wear. It is observed that these phases are followed by βo,α2 and γ in decreasing order of hardness. Therefore, the wear resistance of the βo phase may be superior to that of α2 and γ phases under the present conditions. Meanwhile, the presence of βo phase makes the alloy prone to plastic deformation during grinding, thereby maintaining a relatively stable friction coefficient value even under a high load of 5~10N.