So, in reading many posts over the last few days along with looking through some specs in HTG, I was wondering if anyone has done any definitive research on how low temperature thermal cycling affects knives. The case I have in mind is knives that are regularly run through a dishwasher.
As far as I understand it, repeated exposure to 140-180 cycles of around 1-2hours for several years should temper the blade, causing the softening/destruction of the martensite crystals. If I interpret Verhoeven and HTG correctly, we temper at 300-500 for 1 hour cycles because that is a useful way to control the temperature in cross section, and still accomplish tempering in a reasonable period of time to avoid stabilizing any RA. I have also read (somewhere?) that if you bake a knife at 300°F for a longer period, softening continues past the target HRC. So, it seems that by running a knife through a dishwasher many times at lower temperatures should effect the temper over time. Some quick estimates for a 1.5 hour dishwasher cycle, 3 times a week for a year indicates 156 hours of heating over 104 cycles seem to indicate that if the crystal structure is affected, even slightly, at lower temperatures that the blade soften due to the immense time spent heated.
If anyone has a hardness tester, a test of this would be relatively easy I think. Find a set of knives (my mom has some cutcos that fit the criteria) and test the hardness of a rarely used knife vs a favorite one, you could see if there was any difference. Also, is my theory correct?
As far as I understand it, repeated exposure to 140-180 cycles of around 1-2hours for several years should temper the blade, causing the softening/destruction of the martensite crystals. If I interpret Verhoeven and HTG correctly, we temper at 300-500 for 1 hour cycles because that is a useful way to control the temperature in cross section, and still accomplish tempering in a reasonable period of time to avoid stabilizing any RA. I have also read (somewhere?) that if you bake a knife at 300°F for a longer period, softening continues past the target HRC. So, it seems that by running a knife through a dishwasher many times at lower temperatures should effect the temper over time. Some quick estimates for a 1.5 hour dishwasher cycle, 3 times a week for a year indicates 156 hours of heating over 104 cycles seem to indicate that if the crystal structure is affected, even slightly, at lower temperatures that the blade soften due to the immense time spent heated.
If anyone has a hardness tester, a test of this would be relatively easy I think. Find a set of knives (my mom has some cutcos that fit the criteria) and test the hardness of a rarely used knife vs a favorite one, you could see if there was any difference. Also, is my theory correct?
