Soft Spots in Carburized Product
Soft Spots in Carburized Product
(OP)
thread330-12001: Carburized Soft Spots
Hello all! I'm currently experiencing issues with soft spots on carburized producted due to surface masking (confirmed by metallographic examination, hardness testing, carbon analysis, etc.) - similar to that described in the referenced thread above.
Some background - the product is machined with a water-based coolant, and is run through a pre-heat before carburization, and is not stacked. The process is well monitored at all stages, and records show that temperatures, gas concentrations, etc. were all spot-on when product in question was run. According to the company producing the coolant, our preheat temperature is sufficient to burn off coolant.
I've been able to replicate the phenomenon by intentionally applying machining coolant to the surface of product prior to carburization. While I'm not ruling out other potential causes of these soft spots, I feel pretty confident that this is something that needs further examination. Which brings me to my question: In the time since the ban of solvent-based coolants, what has your experience been with water-based coolants masking carburized product, and what have you found to be successful in mitigating the phenomenon?
For what it's worth, I've been considering the following:
-Increased pre-heat temperatures/time to burn off any reaction product that may form if coolant sits on the surface for a while
-Chemically cleaning/rinsing product prior to carburizing
-Adding in-line machining coolant monitoring systems to better control the coolant itself
Any and all feedback is appreciated. Thanks!
Hello all! I'm currently experiencing issues with soft spots on carburized producted due to surface masking (confirmed by metallographic examination, hardness testing, carbon analysis, etc.) - similar to that described in the referenced thread above.
Some background - the product is machined with a water-based coolant, and is run through a pre-heat before carburization, and is not stacked. The process is well monitored at all stages, and records show that temperatures, gas concentrations, etc. were all spot-on when product in question was run. According to the company producing the coolant, our preheat temperature is sufficient to burn off coolant.
I've been able to replicate the phenomenon by intentionally applying machining coolant to the surface of product prior to carburization. While I'm not ruling out other potential causes of these soft spots, I feel pretty confident that this is something that needs further examination. Which brings me to my question: In the time since the ban of solvent-based coolants, what has your experience been with water-based coolants masking carburized product, and what have you found to be successful in mitigating the phenomenon?
For what it's worth, I've been considering the following:
-Increased pre-heat temperatures/time to burn off any reaction product that may form if coolant sits on the surface for a while
-Chemically cleaning/rinsing product prior to carburizing
-Adding in-line machining coolant monitoring systems to better control the coolant itself
Any and all feedback is appreciated. Thanks!





RE: Soft Spots in Carburized Product
RE: Soft Spots in Carburized Product
If your parts are semi fininshed, a light zirconite blast will usually do the job of removing the conamination off the surface. If you are using any stop-off paints be carefull with the application. If it is applied too thick, a skin forms and the inside remains liquid. When heated in the furnace it bursts spraying the paint on the gear surfaces.
John
Denial ain't just a river in Egypt...Mark Twain
RE: Soft Spots in Carburized Product
Swall - do you mind sharing with me what coolant you've had success with? We're currently using a coolant that we're not tremendously satisfied with (giving us poor tool life, expensive, etc.) and I wouldn't mind running trials with new coolants.
jsokal - I'm not certain what the composition of our coolant is, but I'll be talking to the producer here shortly to try and get a handle on it. If I find anything interesting I'll repost and share.
RE: Soft Spots in Carburized Product
RE: Soft Spots in Carburized Product