powder coating

[jinsokuknives]

hi im new to these forums and i have a question. does powder coating a blade after heat treatment make it softer? i just semi finished a blade i want to have powder coated, but im worried it might through off the hardness. sorry if this is the wrong place. thanks

 

[yablanowitz]

Welcome to Bladeforums! I don't know a lot about powder coating, but if the temperatures I was told by a man who does it for a living are correct, it could kill your heat-treat, especially on low-alloy steel. Some of the high end stainless steels that need extreme high temperature soak might survive.

 

[knarfeng]

hi im new to these forums and i have a question. does powder coating a blade after heat treatment make it softer? i just semi finished a blade i want to have powder coated, but im worried it might through off the hardness. sorry if this is the wrong place. thanks

That depends on the blade alloy and the powder coating. Most alloys require time at ~400F to affect the temper. But the critical temperature does vary with the alloy, so you need to find out the alloy.

The term "powder coating" isn't vary exclusive. It describes an application and cure method rather than the chemistry of the paint. That means that different powder coatings can have vastly different properties and can require vastly different temperatures for cure.

1) determine the alloy of which the blade is made
2) determine the tempering temp. Look at a steelmaker's web site to find the tempering schedules.
3) find out what the cure time and temp are for the "powder coating"
4) If the cure temp of the poweder coating is significantly below the tempering temp, you should be OK.

 

[me2]

As said, it depends on the powder and alloy in question. I've tempered some 1095 blades at 325 F, and most powder coats cure right at or above that, so for that 1095 recipe, it could soften the blade. Most blade steels are tempered at temperatures higher than that, 400 F minimum. I used Brownells spray on powder coating to cover a Cold Steel scalping knife, the Carbon V version from years ago. The recommended temperatures were in the 350 F range for half an hour or so. I dont believe I did anything to the blade, since it was most likely tempered above that. A tip in case you dont already know. Sandblasting is a must if you use the Brownells, and I imagine any other bake on coating. Roughing it up on a coarse belt doesnt even come close to the grip sandblasting will give you on the coating. Blasting with coarse playground sand will do the trick. Bead blasting may work, but I've not tried it. It seems a little too fine, but maybe someone has tried and gotten good results.

 

[jinsokuknives]

ok thank you guys! the knife is made of D2 tool steel and if i remember correctly they cooked at 400 for 30 minutes. ill check later and make sure though. and i tempered the blade at whatever temperature it was when it lost its magnetic quality.. so alot more than 400.