The dispersion of life of bonded MoS2 solid lubricant coatings

Solid lubricant coatings usually fail quite suddenly and thus, for a given specimen, a well-defined life can be measured. Failure may be caused by a number of physical processes, e.g. wearing through the coating, loss of adhesion to the substrate or fatigue. Wear tests of 70 specimens with similarly loaded MoS₂ coatings are analysed. The coating life (in cycles) was in general proportional to the thickness and inversely proportional to the load and amplitude, but there was considerable scatter. The results could be expressed in terms of a specific wear rate fitting a mixed Weibull distribution.