What Are the Main Areas of Wear for Mechanical Seals?

Damage is a common and ineffective way for mechanical seals to fail. Understanding the regularity of mechanical seal damage, estimating wear rates, and finding ways to increase wear resistance and prolong service life are key issues. The main forms of wear that may appear on friction surfaces are adhesive wear, abrasive wear, fatigue wear, fretting wear, and corrosive wear.

Adhesive wear of mechanical seals

Due to the existence of rough micro-protrusions on the surface, the contact of the surface occurs at dispersed micro-protrusions. During friction, direct contact between metals may occur when the lubricating film and surface film rupture, and the connection points are constantly sheared and new connection points are formed. If shearing occurs on the node interface, there will be no wear on both surfaces; if it occurs inside the metal, surface metal transfer, damage, and wear will occur. Metal transfer is the main feature of adhesive wear.

Abrasive wear of mechanical seals

Abrasive wear is a common form of wear of mechanical seal parts, accounting for about half of the total wear. Abrasive wear is caused by hard particles or microprotrusions on relatively hard surfaces causing surface abrasions and material peeling during frictional motion. Abrasive wear is a "microscopic cutting process." Abrasive particles cause alternating deformation of the surface layer material, creating alternating contact stress, which causes fatigue damage to the surface. However, the mechanical action of abrasive particles on the surface always dominates.

Fatigue wear of mechanical seals

Under the action of alternating stress on the friction surface, surface materials are damaged due to fatigue, and parts such as gears and rolling bearings often have this type of damage. The fatigue crack may occur at the point of maximum shear stress under the contact surface, because the plastic deformation is most severe at that point. The cracks that appear first will extend in the direction of the maximum shear stress towards the surface, ultimately causing fatigue wear. The fatigue of the surface material caused by alternating stress and material transfer is called fatigue wear, which is sometimes called contact fatigue.

Fretting wear of mechanical seals

The wear phenomenon between surfaces caused by very small relative vibrations is called fretting wear. If the chemical reaction between the two surfaces mainly plays a role during the formation of this type of wear in mechanical seal spare parts, it is called fretting corrosion wear. If there is a certain pressure between the surfaces in contact causing adhesion of the surface microprotrusions, and these adhesion points are continuously sheared due to small external vibrations, the adhesion points gradually oxidize and red-brown iron trioxide wear debris is formed. In this process, the oxidized wear debris separates from the body, the adhesion point is destroyed, and these wear debris also act as abrasives, causing abrasive wear to the contact surface. When the wear area continues to expand, complete destruction of the contact surface occurs. This is the mechanism of fretting wear formation.

Corrosive wear of mechanical seals

The wear process mainly caused by chemical or electrochemical reactions on the surface is called corrosive wear. The wear of mechanical seal spare parts is moderate in general during corrosion. However, because of the corrosive effect, serious consequences may occur, especially in high temperature or humid environments, where this type of wear intensifies.