Wear, a form of surface deterioration, is a factor in a majority of component failures. This article is primarily concerned with abrasive wear mechanisms such as plastic deformation, cutting, and fragmentation which, at their core, stem from a difference in hardness between contacting surfaces. Adhesive wear, the type of wear that occurs between two mutually soluble materials, is also discussed, as is erosive wear, liquid impingement, and cavitation wear. The article also presents a procedure for failure analysis and provides a number of detailed examples, including jaw-type rock crusher wear, electronic circuit board drill wear, grinding plate wear failure analysis, impact wear of disk cutters, and identification of abrasive wear modes in martensitic steels.

Engineered components fail predominantly in four major ways: fracture, corrosion, wear, and undesirable deformation (i.e., distortion). Typical fracture mechanisms feature rapid crack growth by ductile or brittle cracking; more progressive (subcritical) forms involve crack growth by fatigue, creep, or environmentally-assisted cracking. Corrosion and wear are another form of progressive material alteration or removal that can lead to failure or obsolescence. This article primarily covers the topic of abrasive wear failures, covering the general classification of wear. It also discusses methods that may apply to any form of wear mechanism, because it is important to identify all mechanisms or combinations of wear mechanisms during failure analysis. The article concludes by presenting several examples of abrasive wear.

A hypoid pinion made from 4820 Ni-Mo alloy steel was the driving member of a power unit operating a rapid transit car. The pinion had been removed from service at the end of the initial test period because it showed undue wear. The mode of failure was severe abrasive wear. The cause of failure was insufficient surface hardness, resulting from improper heat treatment. A service recall for the remaining pinions was immediately initiated.

A high-chromium white cast iron shell liner installed in an ore crusher sustained impact damage in the course of operation. Visual-optical examination revealed horizontal cracks on the surface of the liner along with particles that had fractured off. Metallographic examination indicated a heavily deformed surface layer with chip formation at the wear surface. The chemical composition of the liner was found to be Fe-2.74C-0.75Mn-0.55Si-0.51Ni-19.4Cr-1.15M. This alloy is highly resistant to abrasive wear, yet at the same time, prone to chipping because little plastic displacement will occur at the surface. The liner failed as a result of severe abrasion caused by the impact of taconite rock. This was a material-selection problem in that the wrong alloy was used for a condition not anticipated in the original choice.

River water was pumped into a brine plant by a battery of vertical pumps, each operating at 3600 rpm and at a discharge pressure of 827 kPa (120 psi). The pumps were lubricated by means of controlled leakage. The 3.8 cm (1 in.) OD pump sleeves were made of an austenitic stainless steel and were hard faced with a fused nickel-base hardfacing alloy (approximately 58 HRC). Packing for the pumps consisted of a braided PTFE-asbestos material. After several weeks of operation, the pumps began to leak and to spray water over the platforms on which they were mounted at the edge of the river. Analysis supported the conclusions that the leaks were caused by excessive sleeve wear that resulted from the presence of fine, abrasive silt in the river water. The silt, which contained hard particles of silica, could not be filtered out of the inlet water effectively.

Failure of a case hardened steel shaft incorporated fuel pump in a turbine-powered aircraft resulted in damage to the aircraft. The disassembled pump was found to be dry and free of any contamination. Damage was exhibited on the pressure side of each spline tooth in the impeller and the relatively smooth cavities and undercutting of the flank on this side indicated that the damage was caused by an erosion or abrasion mechanism. A relatively smooth worn area was formed at the center of each tooth due to an abrasive action and an undulating outline with undercutting was observed on the damaged side. Particles of sand, paint, or plastic, fibers from the cartridge, brass, and steel were viewed in the brown residue on the filter cartridge under a low power microscope and later confirmed by chemical analysis. Large amount of iron was identified by application of a magnet. It was concluded that the combined effect of vibration and abrasive wear by sand and metal particles removed from the splines damaged the shaft. Case hardened spline teeth surface was recommended to increase resistance to wear and abrasion.

The 16 mm diam 6 x 37 fiber-core improved plow steel wire rope on a scrapyard crane failed after two weeks of service under normal loading conditions. This type of rope was made of 0.71 to 0.75% carbon steel wires and a tensile strength of 1696 to 1917 MPa. The rope broke when it was attached to a chain for pulling jammed scrap from the baler. The rope was heavily abraded and several of the individual wires were broken. a uniform cold-drawn microstructure, with patches of untempered martensite in regions of severe abrasion and crown wear was revealed by metallographic examination. As a result of abrasion, a hard layer of martensite was formed on the wire. The wire was made susceptible to fatigue cracking, while bending around the sheave, by this brittle surface layer. The carbon content and tensile strength of the wire was found lower than specifications. As a corrective measure, this wire rope was substituted by the more abrasion resistant 6 x 19 rope.