Powder metallurgy has been around years. On paper it looks good but in practice it's rubbish.
I get loads of shafts in that have been metal sprayed, some of the time it doesn't stick properly but the main problem is it's a powder and is always a powder all the heat does it bond it and not weld it to the parent metal.
If applied to say a large bearing surface on a shaft and there is anything like depth the action of running hammers the new surface out and you get a loose bearing and a dumbell on either side of the bearing.
This is a classic example on some stainless pump shafts. Bearing size is 40mm to give an idea of scale.

The threads / rings underneath are to give more surface area and grip to the metal spraying but as you can see it doesn't work.
Another disadvantage is when this powder is machined off it's highly toxic and you need very good breathing gear, not a simple mask or you will spend two day gasping .
Personally I love metal spraying, it earns me some serious coin, making good these cock ups. 