堆焊熔敷层表面纳米晶层摩擦磨损性能研究

Friction and Wear Behaviors of Nanocrystalline Surface Layer Prepared on Deposited Layer

用预压力滚压技术在堆焊修复层表面制备纳米晶层.利用TEM、SEM分析技术研究表面纳米晶层微观结构,利用CETR-3型多功能摩擦磨损试验机考察在干摩擦条件下堆焊层表面纳米晶层的摩擦磨损性能.结果表明堆焊修复层表面经表面纳米化处理后,表面形成厚度约为10μm(晶粒尺寸小于100 nm)的纳米晶层,最表面层平均晶粒尺寸约为10 nm.纳米压痕试验表明纳米晶层的硬度提高,最表面纳米晶层的硬度约为原始堆焊层硬度的3倍.与原始堆焊试样相比,表面纳米化试样的摩擦系数降低了10%,磨损体积降低了25%~30%左右.表面纳米化样品的磨损机制由原始堆焊层的磨粒磨损和黏着磨损转变为磨粒磨损,分析表明晶粒细化导致的高硬度、低塑性是摩擦磨损性能改善和磨损机制改变的主要原因.

A nanocrystalline surface layer was fabricated on a deposited layer by using pre - forceing rolling technology. The microstructural features of the treated surface layer were characterized using scanning electron microscopy and transmission electron microscopy observations. The tribological behavior of the nanocrystalline surface layer was investigated under dry conditions by using CETR - 3 tribo - meter. The grain size of the nanocrystalline surface layer of about 10 p^m thickness was about 10 nm in the top surface layer. Nanoindentation tests indicate the hardness of the top nanocrystalline layer was about 3 times of that of the matrix. Experimental results show that the friction coefficients and wear volume of the surface nanocrystallized samples were lower than those of the untreated samples. The friction coefficient and wear volume were reduced approximately by 10% , 28%. After surface nanocrystallization, the dominant wear mechanism was abrasive wear rather than abrasive wear and adhesive wear. The advantages in the friction and wear properties of the treated sample may be attributed to the enhancement of both the hardness and the surface activity by the grain refinement, which, in turn, result in the improvements in producing oxide layer and resistance to plastic removal.