According to Eastern Tool Steel Services: "Toughness, as considered for tooling materials, is the relative resistance of a material to breakage, chipping, or cracking under impact or stress. Toughness may be thought of as the opposite of brittleness. Toughness testing is not as standardized as hardness testing. It may be difficult to correlate the results of different test methods. Common toughness tests include various impact tests and bend fracture tests.
In impact testing, a small sample is held in a fixture and fractured by a moving impacter, such as a calibrated weight on a pendulum. Toughness is reported as the amount of energy, usually measured in foot-pounds or joules, that the sample absorbs before it breaks. Brittle materials will absorb little energy before fracturing. In bend fracture testing, a fixtured sample is subjected to gradually increasing amounts of pressure, usually side or bending pressure, until it breaks.
Most tool steels are notch-sensitive, meaning that any small notch present in the sample will permit it to fracture at a much lower energy. Solid carbide is even more notch-sensitive than tool steels. Thus, in addition to inherent material properties, the impact resistance of tool components is significantly impaired by notches, undercuts, geometry changes, and other common features of tools and dies."
Have found lots of Charpy ratings of various tool steels on the web, but none for stainless steels. Except a comparison from Crucible's CPM S30V with 154CM and 440C. Here are some:
Steel-Hardness-Impact Toughness
S7--------57---125 ft-lb
CPM 3V----58----85
CPM 3V----60----70
CPM 3V----62----40
A2--------60----40
CPM S30V--58----28
154CM-----58----28
440C------56----26
D2--------60----21
CPM S90V--58----19
CPM S60V--56----16
440C------58----16
Notice how the hardness rating can affect toughness. Does anyone have Impact ratings for BG-42, ATS-34, AUS-10, AUS-8, AUS-6, 440A and other stainless steels? Guess that is why S7 is excellent for swords and stainless is not!
In impact testing, a small sample is held in a fixture and fractured by a moving impacter, such as a calibrated weight on a pendulum. Toughness is reported as the amount of energy, usually measured in foot-pounds or joules, that the sample absorbs before it breaks. Brittle materials will absorb little energy before fracturing. In bend fracture testing, a fixtured sample is subjected to gradually increasing amounts of pressure, usually side or bending pressure, until it breaks.
Most tool steels are notch-sensitive, meaning that any small notch present in the sample will permit it to fracture at a much lower energy. Solid carbide is even more notch-sensitive than tool steels. Thus, in addition to inherent material properties, the impact resistance of tool components is significantly impaired by notches, undercuts, geometry changes, and other common features of tools and dies."
Have found lots of Charpy ratings of various tool steels on the web, but none for stainless steels. Except a comparison from Crucible's CPM S30V with 154CM and 440C. Here are some:
Steel-Hardness-Impact Toughness
S7--------57---125 ft-lb
CPM 3V----58----85
CPM 3V----60----70
CPM 3V----62----40
A2--------60----40
CPM S30V--58----28
154CM-----58----28
440C------56----26
D2--------60----21
CPM S90V--58----19
CPM S60V--56----16
440C------58----16
Notice how the hardness rating can affect toughness. Does anyone have Impact ratings for BG-42, ATS-34, AUS-10, AUS-8, AUS-6, 440A and other stainless steels? Guess that is why S7 is excellent for swords and stainless is not!