Friction and wear studies of AISi liners

AlSi liners in internal combustion engines are heterogeneous and highly stressed mechanical parts. Due to reduction of weight, more and more liners are built using hypereutectic AlSi alloys. With respect to tribology, however, AlSi liners scratch the limits of wear rate, system stability and sensitivity to external influences as for example fuel wetting in direct injection engines. One of the most problematic phases is the running-in where the silicon primary crystals are subjected to a drastic grain size reduction forming a mechanically alloyed compound. With the help of a newly designed piston ring/liner simulator friction and real-time wear were measured for entire rings versus liner segments. In addition, high resolution microscopy and chemical analysis were applied to study the grain size reduction as well as the influence of engine oil and of fluel-diluted oil. The precise control of the acting forces allowed to quantify the onset of the tribo-mechanical alloying process.AlSi liners in internal combustion engines are heterogeneous and highly stressed mechanical parts. Due to reduction of weight, more and more liners are built using hypereutectic AlSi alloys. With respect to tribology, however, AlSi liners scratch the limits of wear rate, system stability and sensitivity to external influences as for example fuel wetting in direct injection engines. One of the most problematic phases is the running-in where the silicon primary crystals are subjected to a drastic grain size reduction forming a mechanically alloyed compound. With the help of a newly designed piston ring/liner simulator friction and real-time wear were measured for entire rings versus liner segments. In addition, high resolution microscopy and chemical analysis were applied to study the grain size reduction as well as the influence of engine oil and of fluel-diluted oil. The precise control of the acting forces allowed to quantify the onset of the tribo-mechanical alloying process.