Superficial Rockwell hardness tests

The Rockwell hardness tests (superficial and standard) measure the depth of the impression made by either a 1/8-in. ball, a 1/16-in. ball, or a brale, diamond-point penetrator under major loads of 15, 30, 45, 60, 100, or 150 kg, depending on the type of test (Figure 15.39). The minor load for the Rockwell superficial test is 3 kg, and for the Rockwell standard test 10 kg. 

Rockwell Hardness and Rockwell Superficial Hardness of Metallic Materials Test Method for Vickers Hardness of Metallic Materials Test Method Microhardness of Materials... 

The indenter/load combinations used for superficial Rockwell testing are Hsted in Table 5. As with the standard Rockwell test it is necessary to include the superficial load/indenter combination used for the hardness number to be meaningful, eg, HR30N 65 or HR30T 65. 

Depth of penetration Rockwell superficial and Rockwell standard hardness tests... 

Method for Rockwell superficial hardness test (N and T Scales). 

Another micro-hardness test is the Knoop Hardness Test (henceforth KHT, discussed below). It is worth mentioning that superficial Rockwell tests are also used for ceramics measurements. Hardness tests have been upgraded by the application of instrumented Knoop and Vickers hardness measurements. 

This section has emphasized the most widely used techniques for hardness determinations. In fact, all the other known hardness measurement techniques (see [13]) may be adopted under appropriate conditions for the determination of the resistance of ceramics to indentation. Specifically, the superficial Rockwell method is useful for testing hard tiles, but is beyond the scope of this section. 

With this system, a hardness number is determined by the difference in depth of penetration resulting from the application of an initial minor load followed by a larger major load utilization of a minor load enhances test accuracy. On the basis of the magnitude of both major and minor loads, there are two types of tests Rockwell and superficial Rockwell. For the Rockwell test, the minor load is 10 kg, whereas major loads are 60,100, and 150 kg. Each scale is represented by a letter of the alphabet several are listed with the corresponding indenter and load in Tables 6.5 and 6.6a. For superficial tests, 3 kg is the minor load 15, 30, and 45 kg are the possible major load values. These scales are identified by a 15, 30, or 45 (according to load), followed by N, T, W, X, or Y, depending on the indenter. Superficial tests are frequently performed on thin specimens. Table 6.6b presents several superficial scales. 

Hardness is a measurement of material resistance to plastic deformation in most cases. It is a simple nondestructive technique to test material indentation resistance, scratch resistance, wear resistance, or machinability. Hardness testing can be conducted by various methods, and it has long been used in analyzing part mechanical properties. In reverse engineering, this test is also widely used to check the material heat treatment condition and strength, particularly for a noncritical part, to save costs. The hardness of a material is usually quantitatively represented by a hardness number in various scales. The most utilized scales are Brinell, Rockwell, and Vickers for bulk hardness measurements. Knoop, Vickers microhardness, and other microhardness scales are used for very small area hardness measurements. Rockwell superficial and Shore scleroscope tests are used for surface hardness measurements. Surface hardness can also be measured on a nanoscale today. 

Hardness measurements were made on a Rockwell superficial tester on thp 15-N scale. All hardness measurements were conducted at room temperature. Those values reported in Table I were taken on the base metal prior to testing values reported in Tables II through VII were taken near the fractured edge of all the tensile specimens and reported as averages for each of the corresponding temperatures. 

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