Both individual mechanical seal face material properties and the tribological pair must be taken into consideration.The ideal mechanical face seal materials can be characterized as the following:friction resistance,minimizing leakage,producing low friction,high strength,good thermal properties,corrosion resistance.Mechanical seal face friction can be divided into 4 types:adhesive,abrasive,corrosive,erosive.Mechanical Seal face wear is from thermal stress or fatigue.Mechanical seal ring wear resistance is directly related to hardness.Mechanical seal adhesive wear is a function of the tribological pair of materials. Corrosive wear is related to the chemical resistance of the mechanical seal face material at an operating temperature.When a mechanical seal is operating in high temperatures, the resulting stresses can cause mechanical seal ring cracks or even complete fractures of the mechanical seal face to develop.Material properties which promote resistance to thermal shock are high strength,low expansion,low modulus of elasticity and high thermal conductivity.In most mechanical seals,the actual seal face separation is strongly related to the surface finish of mechanical seal faces or rings,so mechanical seal face materials with smooth surfaces generally leak less than those with rough surfaces.Leakage of a mechanical seal also lies in the compliance or the ability of the seal faces to match each other,thought of as a function of the mechanical seal face shape.Materials with a low modulus,such as carbon,are more easily made into compliant shapes than materials such as tungsten carbide seal faces or rings.Naturally,the coefficient of friction is a function of the tribological mechanical seal face pair but it also depends on the fluid being sealed.The coefficient of friction also depends on the seal face load and is reduced when the seal leaks.
