Machinery Lubrication

Machinery Lubrication March April 2018

Machinery Lubrication magazine published by Noria Corporation

Issue link:

Contents of this Issue


Page 15 of 86

Adhesive Wear Adhesive wear occurs when excessive speeds, temperatures and loads allow metal- to-metal contact. As the two surfaces meet, the metal welds together. e metal surface may appear scuffed or scored with uneven metal chunks attached to it. Adhesive wear from severe sliding normally involves rectangular particles with striations parallel to the direc- tion of elongation. In its mild state, adhesive wear is known as "frosting" and is typically not a major concern. In the severe state, substantial material may be removed as a result of metal- to-metal contact. is is sometimes referred to as sliding wear or galling. Spalling or Fatigue Wear Spalling or fatigue wear is seen when loading or contamination is heavy. Maximum sheer stresses occur below the rolling contact surface. is creates a pit or dent, also known as a spall. It begins as a crack below the rolling surface and propagates over time to the point where metal particles are generated from the fatigued surface. e particles typically are round spheres and may appear as black circles with shiny centers under a microscope. ey usually are 5-10 microns in size, indicative of bearing fatigue prior to a spalling condition. e spall site produces a weakened state on the surface, and failure can ensue. Fretting Corrosion Fretting corrosion wear occurs between two surfaces as a result of small amplitude oscillations. ese oscillations generate oxide debris, which has the appearance of rust or corrosion, hence the term "fretting corrosion." Under microscopic analysis, the particles are characterized by a red oxide color and a uniform pattern. Another form is a complex type of wear that arises in static, oscillating systems. is also takes place in concert with corrosion. e combination of abrasion from wear debris particles with oxidative corrosion is sometimes called false brinelling due to its similar appearance to small-scale plastic deformation. is frequently is seen in idle equipment that is subject to vibration from transportation or adjacent equipment. Corrosive Wear Corrosive wear is caused by an acidic attack on the equipment's internal surfaces. It creates a layer of corrosion products that are subsequently removed by the sliding action. is is not a wear mechanism from a mechan- ical process, but rather a chemical process. e particles, which are normally less than 1 micron in size, will align themselves on the outside edges of a ferrogram. e surface wear pattern is usually even and uniform. In conclusion, wear debris analysis is a valuable tool that can complement an in- service oil analysis program. While it may not be necessary for all assets, critical equipment can benefit greatly from this type of testing. ML VISCOPLEX® paraffin inhibitor keeps crude oil flowing no matter the temperature. Reduce wax buildup inside your pipes and move crude using less power with Evonik's environmentally friendly solution for improved viscosity. Go green and go with the flow. The Oil Additives specialists at Evonik ― Let it flow. A green light for improved flow. ML www . | March - April 2018 | 13

Articles in this issue

Links on this page

Archives of this issue

view archives of Machinery Lubrication - Machinery Lubrication March April 2018