Titanium Nitride Coating a bad Idea?
Titanium Nitride Coating a bad Idea?
(OP)
The company I'm doing an internship with has had problems with drill bits cracking. They are made from 17-4 PH Condition H900 and are coated in TiN.
Apparently the process of coating the bits is affecting the hardness and shape of the bits.
I've contacted several vendors to see if the coating process is a plausible explanation for the hardness issues, and have gotten mixed responses.
Is it possible the process of the TiN coating is affecting the hardness of the bit in a negative way? If so why? Would using 455 SS H900 be a solution?
Thanks.
Apparently the process of coating the bits is affecting the hardness and shape of the bits.
I've contacted several vendors to see if the coating process is a plausible explanation for the hardness issues, and have gotten mixed responses.
Is it possible the process of the TiN coating is affecting the hardness of the bit in a negative way? If so why? Would using 455 SS H900 be a solution?
Thanks.





RE: Titanium Nitride Coating a bad Idea?
Hardening of metals is usually accomplished by heat treatments and anneals. Mess with that, and you lose.
TiN is presumably a hard material. In order to get a hard material onto an oddly shaped surface, there would have had to been thermal changes.
Presumably, some people understand the issues and can tailor their processing to not degrade the performance of the substrate materials.
TTFN
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RE: Titanium Nitride Coating a bad Idea?
There are two processes for depositing TiN coatings: PVD and CVD. PVD process temperatures are in the range of 300-900 F (150-500 C) while CVD processes are much higher, in the range of 900-1100 C (1650-2000 F). PVD processes usually do not result in a hardness decrease or in dimensional change, while CVD processes certainly will reduce the strength of 17-4 PH in the H900 condition.
I suggest you determine which process was used, while also confirming the nature of the failure: brittle fracture? overheating? Coating delamination? There are numerous potential causes, and a full metallurgical evaluation should be performed in order to understand the failure mode. This usually costs less than $2000 for evaluating a handful of parts for hardness, microstructure, and fractography using SEM. Without understanding the root cause it is unlikely the just changing to 455 H900 will solve the issue.
RE: Titanium Nitride Coating a bad Idea?
RE: Titanium Nitride Coating a bad Idea?
RE: Titanium Nitride Coating a bad Idea?
If it's CVD, you may look at sending these out to a lab for microstructural analysis. At the CVD processing temp, maybe you're seeing a pickup of nitrogen along the grain boundaries that's causing embrittlement in the grain structure? That's where a metallurgist will help.
RE: Titanium Nitride Coating a bad Idea?
These bits are used in the medical field during knee replacements.
Everyone,
Thank you all for the information and suggestions
RE: Titanium Nitride Coating a bad Idea?