Heat Treating 17-4

We are a medical device manufacturer, machining mostly aluminum & stainless steels (303, 416, 440c and 17-4PH). We send our components outside for heat
treat, the vast majority of which is 17-4PH H900. We are looking at purchasing a small heat treat oven (about 12 x 12 x 20) and doing the 17-4PH heat treatment in-house.
Our current supplier does our parts in a vacuum oven with an Argon atmosphere. On the 400 series this consistently results in bright, scale free parts, but with the 17-4PH it is not unusual to have slight discoloration. They have told us that it is the nature of this material and they can't guarantee that scale will not build up.
Of course, management doesn't want to spend a lot of money to do this. My preliminary research shows there are ovens out there that have argon or nitrogen atmosphere options, but I'm not sure if they would be sufficient to do the job.
Has anyone had experience heat treating 17-4PH in an inert atmosphere ? If so, how successful have you been at preventing scale build up? Any recommendations for reliable oven manufacturers ?
Any help or advice is greatly appreciated
Kelly
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Kelly:
There currently is a discussion thread on pretty much this topic going on at the Heat Treating Forum on the Ask ASM section of the ASM International Web site (www.asminternational.org). The thread is titled "Discoloration of vacuum heat treated stainless steel". Check it out! Click the ASM ASM button in the upper right, then select the forum near the upper left.
Although ASM International currently bills itself as The Materials Information Society its roots are in heat treatment of metals, particularly steels. This technical society began many moons ago in the American midwest as the steel treater's club, then the American Society for Steel Treatment, and then the American Society for Metals (ASM).
Pittsburgh Pete
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