Calculations

How to Calculate Thermal Spray Deposition, Feedstock, and Cycle Time

A step-by-step walk through the five formulas that govern a thermal spray job: deposition rate, feedstock consumption, spray time per part, thickness buildup, and grind stock.

Every thermal spray estimate starts from deposited volume, so fix that first. Volume equals coating area times as-sprayed thickness. A pump sleeve 80 mm in diameter and 200 mm long has a coated area of pi times 0.08 times 0.20, which is 0.0503 square meters, or 503 square centimeters. At a target thickness of 0.30 mm you deposit 503 times 0.030, which is 15.1 cubic centimeters. Multiply by as-sprayed density, not solid density, since coatings carry porosity. A WC-Co coating at roughly 14 g/cc as-sprayed gives 211 grams of deposited mass. The Coating Thickness Buildup calculator handles this step, and every downstream number depends on getting it right.

Deposition rate is feed rate times deposit efficiency, expressed as deposited grams per minute. If an HVOF gun feeds WC-Co powder at 80 g/min and your measured deposit efficiency is 55 percent, the on-part rate is 80 times 0.55, which is 44 g/min. Do not confuse this with gun output. The 80 g/min is what leaves the hopper; the 44 g/min is what actually builds coating. The Deposition Rate calculator returns this figure. Plasma of oxides typically runs 40 to 60 percent efficiency, HVOF carbides 50 to 70 percent, twin-wire arc 65 to 85 percent, and cold spray of ductile metals above 90 percent.

Powder consumption follows directly: divide deposited mass by deposit efficiency to get the mass you must feed. For the 211 gram sleeve coating at 55 percent efficiency, you feed 211 divided by 0.55, which is 384 grams. The 173 gram difference is overspray you paid for but never deposited. The Powder Consumption calculator does this per lot; for a batch of 40 sleeves you feed 40 times 384, which is 15.4 kg. At a WC-Co powder price near 90 dollars per kg, that lot consumes about 1,384 dollars of feedstock, of which roughly 622 dollars is pure overspray loss. The Overspray Loss calculator isolates that wasted fraction.

Wire processes use identical math with different efficiency bands. For twin-wire arc spraying zinc or aluminum, deposited mass divided by efficiency gives fed wire mass. Coat 500 square meters of steel structure to 0.25 mm with aluminum at 2.7 g/cc: deposited mass is 500 times 0.00025 times 2700, which is 338 kg. At 78 percent arc efficiency you feed 338 divided by 0.78, which is 433 kg of wire. The Wire Consumption calculator returns this. Bond coats add a separate layer: a 0.10 mm NiAl tie coat under the topcoat is its own volume-times-density-over-efficiency calculation, which the Bond Coat Usage calculator tracks so you do not forget to buy it.

Spray time per part is deposited mass divided by on-part deposition rate, plus a non-productive allowance. The 211 gram sleeve at 44 g/min needs 211 divided by 44, which is 4.8 minutes of pure gun-on time. Real cells add 8 to 15 percent for indexing, pass-to-pass cooling, and pattern checks, so at 12 percent the schedulable figure is 4.8 times 1.12, which is 5.4 minutes. The Spray Time Per Part calculator applies this allowance. For robot cells with clean part flow, use the low end near 8 percent; manual spraying with frequent re-clamping and cooldown can push the allowance past 20 percent.

As-sprayed coatings are rough and oversized, so you spray above final dimension and grind back. If final radial thickness must be 0.25 mm and grinding removes 0.08 mm to hit surface finish and roundness, you deposit 0.25 plus 0.08, which is 0.33 mm. That extra stock is real feedstock you pay for. Feeding the grind allowance back into thickness buildup, the sleeve deposit grows from 15.1 to 16.6 cubic centimeters, raising fed powder proportionally. The Coating Thickness Buildup calculator lets you sweep grind allowance so you can balance extra powder against grind labor rather than defaulting to a fat 0.10 mm blanket allowance on every job.

Tie the sequence together with a units check, because mixed units cause most calculation errors here. Keep area, thickness, and density in one consistent system. If area is in square centimeters and thickness in centimeters, density must be grams per cubic centimeter, and the product is grams. Deposition rate must be on-part grams per minute to match, and spray time comes out in minutes. When you sweep a variable, change one input at a time: raise deposit efficiency from 55 to 65 percent and the same 211 gram sleeve now needs only 325 grams fed instead of 384, a 15 percent feedstock cut from a single ten-point efficiency gain.

To run a full part end to end, chain the calculators in order. Start with Coating Thickness Buildup for deposited volume and mass including grind allowance, then Deposition Rate for on-part grams per minute, then Powder Consumption or Wire Consumption plus Bond Coat Usage for fed feedstock, then Spray Time Per Part for schedulable minutes, with Overspray Loss quantifying the wasted fraction. Each output feeds the next input, so a change in efficiency or thickness ripples through consistently. That chained view is what separates a defensible process sheet from a datasheet guess that ignores the 30 to 45 percent of feedstock most processes never deposit.

Published 2026-07-01.