One inch test coupons  that is used in thermal spray to test adhesion and they can also be cut to look at the microstructure.
These needs to be positioned as they where a part of the inside wall of the tube/inside bore that are sprayed.

They are held in place in the fixture by seven  small clamps.

Coupon in clamp.

Overwiev of fixture from "tube/bore-opening"

Overwiev of fixture from the side.

The tube wall is then put in place and it is made up out of seven metal sheet segments with a hole in each for the coupon.

Coupons in position.

All seven coupons ande seven wall segments in place.

From the side.

Wall segments are a cheap replaceble part since it will be sprayed on each spray run and this will just add coating each time. 

There is also a ring that can be attached to the wall opening. On this one you could weld a tube to make the fixture "deeper" to simulate spraying deeper into a cavity than what the normal fixture will give you.