Posted by Gordon England (22.214.171.124) on 13:31:35 16/03/06
In Reply to: Re: stop Zirconia from cracking posted by Alexei Goncharov
These problems are usually associated with poor temperature control during spraying and or excessive coating deposit per pass.
"1. Increase the preheat of the part (with the bond coat)" - Only if existing preheat is below 100 C and substrate is compatible with this heat. Part temperature should not go above about 175 C during preheat or spraying.
"2. Reduce the front cooling air jet flow/pressure on coating" - Only if coating/substrate temperature is falling below preheat levels.
"3. Use/increase gun dwell time" - Not sure what you mean here. Assuming you mean a time pause between spray passes to control temperature. I would only consider this if all other forms of temperature control failed.
Ideally, coating/substrate wants a constant uniform temperature throughout the process. Spray particle quenching obviously produces very large temperature gradients, but should be a microscopic effect. These coatings should be applied at less than 0.001" (0.025 mm) per pass which helps control heat input.
Nature of Thermal Spray Coatings
Surface Engineering in a Nutshell
Surface Engineering Forum
Thermal Spray Gun Repair Service
Plasma Consumable Parts
Thermal Spray Powder Supplies
Thermal Spray Coatings on Carbon and Glass Fibre Reinforced Polymers
HVOF Coating of Paper Making Roll
Thermal Spray Processes:
Combustion Wire Thermal Spray Process
Combustion Powder Thermal Spray Process
Arc Wire Thermal Spray Process
Plasma Thermal Spray Process
HVOF Thermal Spray Process
Detonation Thermal Spray Process
Plasma Flame Theory
Cold Spray Coating Process
Wear and Use of Thermal Spray Coatings
Corrosion and Use of Thermal Spray Coatings
Glossary of Thermal Spray and Surface Engineering Terms
Image Directory for Thermal Spray Coatings
Plasma Gas Flow Information
Plasma Gas Flow Correction Calculator
Links to other interesting sites related to thermal spray and surface engineering
Periodic Table of the Elements
Calculators for Conversion between Units of Measurement
Surface Engineering Message Board Archive
Surface Engineering Message Board Archive Index
Search This Site
© Copyright Gordon England