Metal Heat Treating FAQ

Q: What is Plasma Nitriding?  

A: Plasma Nitriding is a heat treatment process that uses energy and nitrogen gas to diffuse nitrogen atoms into the surface of steel parts to create wear resistant compounds.

Q: How is Plasma Nitriding different from Gas and Salt Bath nitriding?

A: Plasma nitriding has the ability to change the ratio of Nitrogen and Hydrogen — increasing nitrogen for alloys with high diffusion rates and lowering it for those that do not. This allows maximum case depth without creating a brittle surface. The glow discharge gives the advantage of penetrating alloys that traditionally will not nitride, such as precipitation hardening and austenitic stainless steels.

Q: What type of case depth can I expect?

A: It all depends. Different alloys diffuse at different rates. Low alloy steels such as 4140 diffuse at a high rate and can achieve case depths of .009"-.012" from a single 40 hour process. The main nitride compounds created are Iron-Nitride. The average surface hardness achieved is 55-58 HRC. High chromium alloys such as H-13 achieve less case depth but with a higher surface hardness because the nitride compounds formed are Chromium-Nitride. Alloys created especially for Nitriding like Nitralloy-135 can achieve depths close to .020" with extended processing time.

Q: Can the inside diameter of a cylinder be nitrided?

A: The rule of thumb is the glow will travel into the bore of a cylinder 3 times the diameter of the bore. For example, a cylinder that is 40" in length with a 3" bore will have 9" from each end with nitriding and the middle will be unaffected.

Q: Can the case depth be measured?

A: Only by sectioning a coupon and performing a etch test or if the case is thick enough a Microhardness test. A coupon will need to be processed along with the parts. The ideal size for a test coupon is 1"rd x 2"lg.

Q: How long does it take for Magnum Metal Treating to complete plasma nitriding once parts are received?

A: Since the process normally takes 40 hours after the furnace is pumped down and the sputtering process is complete, the furnaces are reloaded twice per week. Magnum MT has 2 plasma nitride furnaces so allow 1-2 weeks for your parts to be processed and tested.

Q: I have a new part and don't know how it will react to Plasma Nitriding.

A: The best way to find out is to process a trial run part. Send us a part and we will let it 'tag along' with the next load that has room and you can evaluate if it is the right process for you. We normally don't charge for this service.