润滑相尺寸对自润滑膜形成的影响

Effect of Size Refinement of lubricants on the Formation of Self-Lubricating Films

摘要:

采用高能球磨制备细小的复合粉末，再通过感应烧结制备耐高温自润滑IS304涂层，涂层致密且润滑相明显细化，其中Ag粉尺寸为5 μm左右、氟化物尺寸小于2 μm，且氟化物粒子与Cr2O3粒子形成复合结构。室温时IS304摩擦系数较大，磨损机制主要为微观脆性断裂；随着温度的升高，由于润滑相尺寸减小、且氟化物粒子与Cr2O3粒子形成复合结构，使得摩擦副在高速滑动过程中接触点的瞬态温度迅速升高，此瞬态温度有效地激活了氟化物粒子的润滑性能，在摩擦力和压力的作用下，氟化物粒子经塑性变形后形成表面润滑膜，使得接触面的摩擦系数急剧减小。有限元计算也表明润滑相的细化和分布位置的改变可明显提高润滑相的瞬态温度。

Abstract:

IS304 coating was been prepared by high energy ball milling and induction sintering. The microstructure of IS304 was fine and dense, the sizes of self lubricating particles were very small. Ag particles were about 5 μm, BaF2/CaF2 particles less than 2 μm, while some BaF2/CaF2 particles were located in Cr2O3 particles to form composite structure. Results show that the temperature and microstructure have great effect on the wear rates of the IS304. At 20 °C, the friction coefficient is great. The worn surface showes that the brittle fracture is the dominant wear mechanism. With the increase of temperature, IS304 exhibits an improved friction coefficient in the temperature range from 300 to 350 °C due to the formation of self-lubricating fluoride films. The existence of fluoride film on the worn surface of IS304 is attributed to the size refinement and the appropriate distribution of fluorides, resulting in a higher temperature rise at the instantaneous contacting surface in comparison to that of the PM304. The finite element models with different microstructures were built to simulate the flash temperature.