Hardness Matters

Author:  Professor Dr. David Kirk
Source:  The Shot Peener magazine, Vol 33, Issue 3, Summer 2019
Doc ID:  2019032
Year of Publication:  2019
Abstract:  
INTRODUCTION Hardness, for shot peeners, is resistance to localized plastic deformation induced by impacting shot particles. We therefore have two areas of interest: the hardness of the component being peened and the hardness of the shot particles themselves. The hardness of the component is normally out of our control. One exception is the hardness of the Almen strips that are peened in order to establish the intensity of shot streams. Hardness appears in specifications for both shot particles and Almen strips and therefore requires testing. It is common for peeners to blindly accept specified hardness values and test methods at face value. Unfortunately, hardness testing then becomes a minefield. There are three key areas that need to be considered if we are to be able to navigate through this minefield. These are (1) sample heterogeneity, (2) test method and (3) indent size. Metallurgists are, of necessity, relatively expert at matters concerning hardness testing of metals and alloys.