Understanding Rockwell Hardness Tests and Indenters

The question asks about a specific hardness test that uses a diamond cone or a hard steel ball as the indenter and measures hardness on the HRB or HRC scales. Let's look at the characteristics of different common hardness tests.

Different hardness tests use different types of indenters and measure hardness on different scales:

• Brinell Hardness Test: This test typically uses a hardened steel or carbide ball as the indenter. The hardness is measured on the Brinell Hardness (HB) scale.
• Vickers Hardness Test: This test uses a square-based diamond pyramid indenter. The hardness is measured on the Vickers Hardness (HV) scale.
• Knoop Hardness Test: This test uses a rhombic-based diamond pyramid indenter. It is primarily used for testing brittle materials or thin sheets and measures hardness on the Knoop Hardness (HK) scale.
• Rockwell Hardness Test: This test is unique in that it uses different indenters and different major loads to create various scales (like HRA, HRB, HRC, HRD, HRE, HRF, HRG, HRH, HRK). Specifically:
  • For scales like HRC, HRA, and HRD, it uses a diamond cone indenter (often called a Brale indenter).
  • For scales like HRB, HRE, HRF, HRG, HRH, and HRK, it uses a hard steel ball indenter (typically 1/16 inch, 1/8 inch, or 1/4 inch diameter).
  The test measures the depth of penetration of the indenter under a major load, relative to the penetration under a minor load.

Based on the description provided in the question, which mentions the use of a diamond cone or a hard steel ball and the HRB or HRC scales, the test being described is the Rockwell hardness test.

In summary:

The Rockwell hardness test is the one that specifically uses a diamond cone (for scales like HRC) or a hard steel ball (for scales like HRB) to determine hardness on its characteristic HR scales.