蒸馏水润滑下Si_3N_4-白口铸铁摩擦面上表面膜的分析

The Tribofilm Formation and Its Constituents for Si 3N 4 White Cast Iron Pair Under Distilled Water Lubricant

在环－块磨损试验机上考察了蒸馏水润滑下Ｓｉ３Ｎ４分别与白口铸铁和碳钢（作对比用）配副的摩擦磨损特性．在ＳＥＭ下观察了白口铸铁磨面表面膜的形成过程，用ＸＰＳ、ＦＴＩＲ和ＸＲＤ分析了表面膜的成分、组成与结构，并对其形成机理进行了探讨．结果表明，Ｓｉ３Ｎ４在水润滑下摩擦时磨面上发生了氧化和水解反应：当Ｓｉ３Ｎ４与白口铸铁配副时，由于铸铁中碳化物的剥落而形成剥落坑，Ｓｉ３Ｎ４磨屑嵌入剥落坑并氧化和水解，其反应产物富集于剥落坑中，脱水聚合后形成硅胶，从而在磨面形成具有一定厚度和面积的含硅胶的表面膜，表面膜的形成保护了陶瓷和铸铁磨面，使其变得很光滑，从而使摩擦系数降至０．０２，并使系统磨损率几乎接近于零；当Ｓｉ３Ｎ４与碳纲配副时，由于碳钢没有能力富集Ｓｉ３Ｎ４的氧化和水解产物，故磨面不能形成有效的表面膜，所以其摩擦系数仍然较高。

The friction and wear properties of Si 3N 4 sliding against white cast iron and carbon steel (used for comparison) under distilled water lubricating condition were investigated on a M 200 ring block wear tester. The process of tribofilm formation on the worn surface of white cast iron was observed by means of SEM. The compositions, constituents and constructions of the tribofilm were analyzed by using a combination of several analysis techniques including XPS, FTIR and XRD. Futhermore, the formation mechanism of the tribofilm was explored simply. From the results, it is found that oxidation and hydrolysis reactions occur on the worn surface of Si 3N 4. Tribofilm, which possessing a certain thickness and area, forms on the worn surface when Si 3N 4 slides against white iron. The reason for the film formation is that a part of Si 3N 4 particlies seperated from ceramic specimen are embeded into the pits caused by spalling of carbides on the wearing surface of white iron during the wear test. Then, the particles are oxidized and hydrolyzed in situ, and the resultant is concentrated in the pits and polycondensed into silicasol. The formation of the tribofilm facilitates the surfaces of Si 3N 4 and iron to smooth. As a result, the friction coefficient of the pair is lowered to 0 02, and the wear rates of Si 3N 4 and iron are near zero. For Si 3N 4 carbon steel pair, both friction coefficient and wear amount are still high. The reason is that a useful tribofilm does not emerge on the surface because the steel is not able to enrich the resultant of oxidation and hydrolysis of Si 3N 4.