The only place I now use an incandescent bulb is in my oven. It went out the other day and I was looking for a replacement. I am using LED all over these days but realized it may not be possible to use LEDs in a heated environment like an oven. Is that the case, or are there LED bulbs for that now also?
As already stated, LEDs can't take the heat. In addition:
Many ovens use halogen bulbs instead of "ordinary" incandescent bulbs. These are a type of incandescent light with two key differences: size and heat.
The size is irrelevant for most ordinary lamps but great for an oven, where you want something small so that it won't take away from valuable interior cooking space.
The heat is a huge problem for ordinary lamps, to the extent that there were major recalls/design changes many years ago because of halogen lamps setting curtains and other stuff on fire, resulting in metal grid covers for those lamps and eventually they disappeared altogether in favor of much more efficient CFL and then LED lamps. But heat is perfectly fine in an oven, where you have a high-but-regulated temperature. If you have the light on while cooking and it puts a few extra watts of heat into the oven, the element will turn off a few seconds earlier and the net energy usage is a big fat 0.
In general with any lighting system, the efficiency is a balance between light and heat. All the energy not turned into light becomes heat. In an oven that is perfectly fine and useful instead of wasteful. For an extreme example of this, where the light bulb is the heating element, see the Easy Bake Oven. In fact, for a conventional electric oven, heat generated from a light bulb is essentially the same efficiency as heat generated from heating elements. Where energy usage is a bit different is with microwave ovens and gas ovens.
Not gonna happen. Can't take the heat.
Those consumer products one calls an "LED light bulb" is a built consumer product made of components - case, heat sink, electronics and an array of LED emitters. The latter are purchasable as components by electronics supply houses such as mouser.com, with over 100,000 types listed. Every one has a data sheet.
You (the builder) merge the LED with a heat sink (probably of your own design). To guide heat sink design, the data sheet calls out thermal limits at the point where the LED meets the heat sink. You can't let the LED get any hotter than that.
Those limits are typically 85C, or in rare instances, 115C. This isn't even 250F. That's not gonna work in an oven.
So that's the end of that. CFLs have similar problems, more owing to the survivability of their electronic ballast.
Incandescent bulbs love heat, so it's not a problem.
Incandescent bulbs require heat to function, and if it isn't already in the environment, they have to make it. They self-regulate and don't need a driver/ballast. So they run very happily in hot places.
It's a match made in heaven, and there's no reason other than OCD/aesthetics to want to reinvent that wheel. (and if you really, really, really wanted to, then "light pipes").
Keeping in mind that oven lights are only on when the oven door is open (and often, when the oven is turned on). So the energy use is trivial, and one would be hard-pressed to save a penny's worth of electricity over the life of an oven. Any effort to "greenify" or "increase efficiency" would be better spent anywhere else. Anywhere. Honestly.
I think it's unlikely that this is possible.
The environment in the oven in quite mild compared with an incandescent lamp, but LEDs, being semiconductor devices generally don't function well above about 100C.
Some vendors seem to be making newer ovens with insulated or otherwise thermally isolated lamp compartments so that they can install LED lighting but generally replacing a standard incandescent bulb in an oven with an LED one will not work.
Even if you could, I wouldn't trust that the plastics, solder and semiconductors of an LED lamp wouldn't leach unfriendly chemicals out into the oven's air, and then into the food. There's a reason they tell hobbyists to not use food ovens for "re-flowing" (building or fixing) electronic circuit boards.
If you want to save energy, you may start from reconsidering the oven itself. It's most likely electric, so basically a huge light bulb, 1000 times greater than the small one you are trying to replace.
And yes, such a replacement is possible. Not with an LED, but there are (gas discharge) lamps with similar efficiency and high operation temperature. They also work much longer (like 10 times).