Abrasive hardness refers to an abrasive's ability to resist localized external forces; it is commonly measured using the Mohs hardness scale-for instance, the Mohs hardness of silicon carbide is approximately 9. Diamond is the hardest known material; this is attributed to its cubic lattice structure, in which carbon atoms are bonded together by exceptionally strong carbon bonds. An abrasive must be harder than the material being processed; the greater its hardness, the stronger its cutting capability. Furthermore, certain abrasives possess unique physicochemical properties. For example, diamond exhibits the highest thermal conductivity of any known material, enabling it to efficiently dissipate the heat generated during grinding. Additionally, diamond is highly chemically inert toward elements of the iron group; however, it is important to note that when grinding ferrous metals, chemical reactions may occur between the carbon in the diamond and the metal, potentially leading to the premature wear of the grinding wheel.
Abrasive grain size refers to the physical dimensions of the abrasive particles. Abrasives are typically classified into four groups based on their particle size: coarse grains, fine powders, micropowders, and ultrafine powders. Among these groups, the grain size of coarse grains and fine powders is designated by the number of mesh openings per linear inch of a sieve screen; this designation is indicated by placing a "#" symbol in the superscript position to the right of the numerical grain size value. Conversely, the grain size of micropowders and ultrafine powders is expressed in terms of the actual physical dimensions of the particles; this designation is indicated by prefixing the numerical particle size value with the letter "W." For superhard abrasives such as diamond, micropowder grades are primarily classified based on parameters such as grain size, purity, surface treatment, and crystal morphology, in order to meet the diverse requirements of various precision machining applications.
Abrasive strength refers to the inherent structural integrity of the abrasive-specifically, the ability of an individual abrasive grain to withstand external forces without fracturing. Sufficient strength is essential for maintaining both the cutting capability and the service life of the abrasive grain. Properties such as toughness or bulk strength can be controlled by adjusting factors such as the composition of the raw material mixture, purity, grain size, and crystal structure, thereby tailoring the abrasive to suit specific applications. For instance, ceramic alumina abrasives produced via the sol-gel method (known as SG abrasives) possess a uniform microcrystalline structure resulting from their specific sintering process. Consequently-while maintaining the same level of hardness-they exhibit significantly greater toughness compared to conventional alumina abrasives, offering distinct advantages such as high strength, excellent self-sharpening characteristics, and an extended service life. Abrasive wear refers to the phenomenon of material loss from a surface caused by relative motion between the object and abrasive particles or asperities; the material loss resulting from this process can account for up to 50% of total wear. Based on the behavior of the abrasive particles, abrasive wear can be classified into two categories: two-body wear and three-body wear.
