Deposition Efficiency Measurement

[deepskysea]

I am going to measure the deposition efficiency of HVOF tungsten carbide coating. My plan is coat half kilo material on the tube with 12 inch length and 6 inch diameter, check the weight difference of the tube before and after the coating. Is that right? Or is there any standard DE measurement method?

[Gordon]

Hi Deepskysea

That sounds good, make sure gun stays over test piece all of the time while spraying . Spraying 500g of material should give very accurate results, but using smaller amounts say 100 - 200g should be adequate (if your weighing scales are reasonable accurate) and less wasteful on expensive powder . If your powder feed hopper is easily detached and not too heavy for your scales, it may be easier to weigh hopper before and after spraying to determine powder used.

[deepskysea]

Thank you Gordon. I know there should be some powder left in the hopper or somewhere else, so do you know whether there is standard for DE measurement.

[Gordon]

Hi Deepskysea

I'm not aware of any standards for deposit efficiency tests. It would be useful to know the powder suppliers procedures for conducting these tests for their data sheets

A procedure I was taught many years ago was using a 5"x7"x1/8" plate, sprayed for 30 seconds. Plate weighed before and after to get coating weight. Powder used was via a separate powder feed rate check for 30 seconds. As you can imagine, not very accurate, also plate and coating would get extremely hot, so probably not very representative of a normal coating anyway. Mind you we were stuck with rather vintage 500g weighing scale so it was difficult to do much else. Total waste of time, brought home when someone reports that he just got 110% DE