Gordon England Surface Engineering Forum



Re: Microhardness of WC/Co coating and optimum gas flow parameters

Posted by Gordon England (62.252.0.12) on 19:07:28 14/04/05

In Reply to: Microhardness of WC/Co coating and optimum gas flow parameters posted by Arturas

: In Reply to: Amorphous phase of WC-12Co coating posted by Arturas
:
: It is very interesting , You said that with increasing fuel gas flow amorphous phases quantity of WC-12Co coating increase and decrease wear resistance , but at the same time coating porosity decrease. So, how to find optimum parameters of gas flow?
: And I got that by increasing heat treatment temperature from 20C up to 600C microhardness of WC-12Co coating a little bit increase (5-10 percent) How to explain it?

To clarify, increasing heat input into WC/Co particles will tend to increase oxidation and production of amorphous phases and other phases not found in original powder. Increasing fuel gas flows will only contribute to this if it is increasing the heating effect. Too little or too much fuel will reduce flame temperature (assuming oxygen is kept constant).

To achieve the best coating for your needs, requires more than just optimising gas flows. Other parameters such as powder feed rate, air flow (if used), spray distance, selecting best nozzle/air cap hardware etc.. Also using the right powder particle size and distribution is critical. Finer powders are more susceptible to these problems than coarser powders.

Optimising parameters is down to conducting spraying trials, ideally only changing one variable at a time and evaluating the coatings. Choose your starting or base line parameters from a known good coating of similar chemistry and particle sizing. No easy task considering all the variables.

Heat treating these coatings is not common practice. Possibly, the increase in hardness may come from amorphous and metastable phases recrystallising producing some W2C and eta carbide phases (not sure if temperature is high enough though).


Follow Ups:


Surface Engineering Forum

Surface Engineering Message Board Archive

Surface Engineering Message Board Archive Index

Search Message Boards Archives

www.gordonengland.co.uk





GoogleCustom Search

Post A Message!

Gordon England Surface Engineering ForumPlease go to the new Surface Engineering Forum as this old message board is a read only archive. Please copy and paste relevant information or link to the page if you wish to reactivate a thread on the new forum.







Gordon England Independent Thermal Spray Coating Consultant
Telephone: +44 (0)1252 405186

PLEASE CLICK HERE TO EMAIL

Site Links

Introducing

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

Applications:

Thermal Spray Coatings on Carbon and Glass Fibre Reinforced Polymers

HVOF Coating of Paper Making Roll

Abradable Coatings

Photomicrographs

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

Contact Form

Links to other interesting sites related to thermal spray and surface engineering

Reciprocal Links

Periodic Table of the Elements

SI Units

Calculators for Conversion between Units of Measurement

Hardness Testing

Surface Engineering Message Board Archive

Surface Engineering Message Board Archive Index

Search This Site


Photography Gallery2

Photography Gallery3


© Copyright Gordon England