I have an idea, thought I would run it by the brain trust. I was thinking of painting knives in Cerakote hi-vis orange. That specific colour is florescent under black light. So if you dropped your knife at night it would glow with the black light and hopefully make it easier to find. I would package the knife with a small keychain black light. But Cerakote ain't cheap, it would add maybe $20 +/- to the cost. The big question is: is the juice worth the squeeze? Let me know what you think, and have a great Easter long weekend.
My day Job is a sales rep for the collision refinish industry. Coatings are a whole new ball game. The prep work and correct spaying technique of Cerakote will be key to your quality control. It will be a new skill to acquire the ability to spray correctly and consistently to get the coverage at the right mil thickness. This will be key to the products performance and cost effectiveness. Apply not enough and the coating will fail and look like crap, and over apply and the same will happen. Cerakote I believe needs to be baked on @ 250F for two hours. Not sure if this length of time would mess with your (let’s say 400F) temper cycle. There is an air dry version of ceramic coatings out there, if this one is available in that then makes it lot less of a concern. As for the coating holding up, check out this video from Aaron Gough. Aaron now uses a DLC (Diamond Like Carbon) finish, and even now some of his knives come back from the professional spray company not looking so good. I’m not warning you off the idea. I like it. And given my background I have considered it myself. As you will see from the video, you will have to be transparent with the customer that Cerakote will scratch and could show rust etc. just like selling a knife with no coating, make sure they know that with use the knife is going to show it’s wear and tear. Good luck and happy Easter to you too Griff Cerekote is tested in this video.
Originally I just wanted to paint the knives orange and Cerakote does make a colour called Hunter Orange in their C-series (air harding) and the H-series (over harding). But then I found the Hi-vis Orange (H-series only) that is florescent , and that's when I fell down the rabbit hole of possible, possibilities of a florescent knife. And just my luck the Hi-vis Orange has the lowest chemical resistance to colour chang in the product line. Might need to clear coat it as well, it's never easy is it. Thank you very much for the advice, if I go through with it I'll keep you posted.
I don't know anything about coatings, but I do think you should be just fine with the 250F for 2 hours curing temp. Tempering is mostly a function of temperature rather than time. Tempering for a long time below your initial temper temp likely wont make much of a difference.
I’d still be hesitant. If you temper a knife at 400F and then for some strange reason the second temper is 350F, whatever Rockwell 350F provides is the final hardness. I’d be worried the knife took on whatever Rockwell 250F gave lol. They tell you to just not exceed your temper when post HT grinding. Though most people do not realize the naked human hand will blister above 125F. So really no worries there if you grind without gloves. Best to dunk the blade just as it gets warm to protect the thinnest part, your heat treated edge. Have to be more careful using a jig of course.
Here's an article I just found discussing tempering time with static temperature. https://www.sciencedirect.com/science/article/pii/S1665642316300013#fig0020 It seems to only have a marginal influence on hardness and toughness, however oddly, it seems with increasing time the hardness actually increases and toughness decreases. This is also a different steel than what we'd use for knives so I'm not sure how well the information would transfer over. Also quite a bit higher tempering temp than we'd use on knives as well. Overall I would like to assume that an additional couple hours at the same or lower tempering temperature than your initial would make only a slight difference. Although I'm really not sure. Maybe ill test it some day.
You know I might float this one to Larrin Thomas, he’s been kind enough to answer before. I’m actually hoping the answer is the lower temp wouldn’t have an effect because I am very interested in using a ceramic coating.
Update, Success! I did two knives made from 440C, and for the scales I used some tan micarta I had laying around. I bought the Cerakote starter kit, it comes with everything you need. I did try to piece the kit together from Amazon and such but in the end it was just easier to get it from Cerakote. For the preparation they recommend media blasting with 100 grit AO, I just used what I had. I can't remember exactly but I am pretty sure what I had was 80 grit and it turned out just fine. Since the coating is mixed by weight and such a small amount is used, I had to buy a scale that was good to 2 decimal places. Scale was less then $20 on Amazon. The paint sprayed on nice - I have used other paints before and this applied very nice in comparison. One I loaned to a guy at work to just try out this hunting season and now he won't give it back . I took the other one hunting this year and after processing a full deer start to finish, there was only 1 superficial scratch in the coating. Experimenting with the florescent aspect, it seemed to work quite well and would definitely help if you happened to drop the knife in the dark. One day I will get things together and post some photos.
