Erosive wear resistance

Leyland, A. and Matthews, A., Thick, Ti/TiN Multilayered Coatings for Abrasive and Erosive Wear Resistance, Surf. Coat. Technol., Wo. 70,1994, pp. 19-25. 

For smaller particle sizes ( 1,000 microns), polyurethanes provide a superior erosive wear resistance to metals at most normal velocities of up to 20m/s. Outside these limits, the materials need to be evaluated in a manner that is as close to real conditions as possible. 

Of these groups, the castable, thermoplastic, and sprayable polyurethanes have the greatest abrasive and erosive wear resistance. 

It is not possible to use nanoindentation methods to obtain information about the impact fracture and erosive wear performance. High hardness can confer improved wear resistance but it is often associated with brittleness and poor toughness and erosive wear resistance. 

B.D. Beake, S.R. Goodes and J.F. Smith, Micro Impact testing A new technique for investigating thin film toughness, adhesion, erosive wear resistance and dynamic hardness, Surface Engineering 17, 187 193(2001). 

In summary, imder conditions of carburization, the erosive wear resistance of the QllOO coating demonstrated superior erosion wear resistance to that of the 25Cr-35Ni-Fe of up to four times. 

Niobium carbide is used as a component of hard metals, eg, mixtures of metal carbides that are cemented with cobalt, iron, and nickel. Along with tantalum carbide, niobium carbide is added to impart toughness and shock and erosion resistance. The spiraling rise in the price of tantalum has spurred the development of a hafnium carbide—niobium carbide substitute for tantalum carbide (68). These cemented carbides are used for tool bits, drill bits, shovel teeth, and other wear-resistant components turbine blades and as dies in high pressure apparatus (see Carbides). 

Types of Wear. There are several distinct types of wear that can be divided into three main categories abrasive wear, sliding wear, and erosive wear. The type of wear encountered in a particular appHcation is an important factor influencing the selection of a wear-resistant material. 

For erosive wear. Rockwell or Brinell hardness is likely to show an inverse relation with carbon and low alloy steels. If they contain over about 0.55 percent carbon, they can be hardened to a high level. However, at the same or even at lower hardness, certain martensitic cast irons (HC 250 and Ni-Hard) can out perform carbon and low alloy steel considerably. For simplification, each of these alloys can be considered a mixture of hard carbide and hardened steel. The usual hardness tests tend to reflect chiefly the steel portion, indicating perhaps from 500 to 650 BHN. Even the Rockwell diamond cone indenter is too large to measure the hardness of the carbides a sharp diamond point with a light load must be used. The Vickers diamond pyramid indenter provides this, giving values around 1,100 for the iron carbide in Ni-Hard and 1,700 for the chromium carbide in HC 250. (These numbers have the same mathematical basis as the more common Brinell hardness numbers.) The microscopically revealed differences in carbide hardness accounts for the superior erosion resistance of these cast irons versus the hardened steels. 

We employ two basic approaches to rate a polymer s wear resistance. In the first, we expose a polymer surface to a standard set of abrasive or erosive conditions and examine the surface for visual evidence of wear. We primarily use this method to qualitatively rank materials. In the second approach, we expose samples to wear inducing conditions and determine wear resistance in terms of weight loss as a function of time. 

Li, J. and I.M. Hutchings. "Resistance of Cast Polyurethane Elastomers to Solid Particle Erosion." Wear 135 (1990) 293-303. 

When there is impinging erosive wear, MDI-based polyethers are normally classified as the most suited because hydrolysis resistance is also taken into account. Certain of the more sophisticated esters have better erosive wear than the high-cost ethers (PTMEG) under hydrolysis conditions. The temperature limitation, however, is still just below that of the ether-based materials. The angle of impingement also must be taken into account. 

The duplex stainless steels are superior to other stainless steels with respect to high resistance to chloride stress corrosion cracking, high mechanical strength, lower thermal expansion than the austenitic grade steels, and good erosion and wear resistance. 

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