Request for solution to reduce porosity in HVOF Tungsten Carbide Coatings
10-09-2012, 01:00 PM,
#1
Request for solution to reduce porosity in HVOF Tungsten Carbide Coatings
Dear Friends,

We are having Flame Spray Technologies make HVOF Spray Gun and when we depositing WC - Co Coatings with this gun, we are achieving porosity in the range of 2 to 2.5 % which is not acceptable for most of the customers.

The porosity should be less than 1%

Kindly suggest the factors which are affecting for higher porosity levels.


Regards,

SREENIVAS
Reply
10-09-2012, 05:56 PM,
#2
RE: Request for solution to reduce porosity in HVOF Tungsten Carbide Coatings
Hi ,

Assuming that you have checked your system, you could work on powder,
several factor could help you to reach the 1% :

Particle size distribution : use the narrowest distribution
Apparent density of the powder, I'm still surprising that this data is missing on several powder provider datasheet.
Primary carbide size included in your agglomerated and sintered powder

If you give more detail, it would be easier to help you.

Regards
Reply
10-10-2012, 10:35 AM,
#3
RE: Request for solution to reduce porosity in HVOF Tungsten Carbide Coatings
(10-09-2012, 05:56 PM)Spraytube Wrote: Hi ,

Assuming that you have checked your system, you could work on powder,
several factor could help you to reach the 1% :

Particle size distribution : use the narrowest distribution
Apparent density of the powder, I'm still surprising that this data is missing on several powder provider datasheet.
Primary carbide size included in your agglomerated and sintered powder

If you give more detail, it would be easier to help you.

Regards


Sir,

Thank you for your reply

Kindly forward the problems in HVOF GUN also which will be cause more porosity in coatings.

Kindly do the needful


Regards,

SREENVIAS

Reply
05-12-2017, 06:11 PM,
#4
RE: Request for solution to reduce porosity in HVOF Tungsten Carbide Coatings
(10-10-2012, 10:35 AM)sreenuvundela Wrote:
(10-09-2012, 05:56 PM)Spraytube Wrote: Hi ,

Assuming that you have checked your system, you could work on powder,
several factor could help you to reach the 1% :

Particle size distribution : use the narrowest distribution
Apparent density of the powder, I'm still surprising that this data is missing on several powder provider datasheet.
Primary carbide size included in your agglomerated and sintered powder

If you give more detail, it would be easier to help you.

Regards


Sir,

Thank you for your reply

Kindly forward the problems in HVOF GUN also which will be cause more porosity in coatings.

Kindly do the needful


Regards,

SREENVIAS

Porosity is typically caused by the flame being too cold. One thing you can try is to increase your O2 & H2 flows to achieve a hotter flame. There will be a balancing act between oxides and porosity, but when you get the parameters set right you should be able to achieve what you're looking for.

Mike
Reply
05-18-2017, 12:03 PM,
#5
RE: Request for solution to reduce porosity in HVOF Tungsten Carbide Coatings
Hi, Sreenvias

What kind of gun do you use exactly?
What are the spray parameters?
Could you post a micrograph oа your coating?
All of these is important to understand the problem

Best regards,
Vig
Reply
05-22-2017, 11:12 AM,
#6
RE: Request for solution to reduce porosity in HVOF Tungsten Carbide Coatings
(10-09-2012, 01:00 PM)sreenuvundela Wrote: Dear Friends,

We are having Flame Spray Technologies make HVOF Spray Gun and when we depositing WC - Co Coatings with this gun, we are achieving porosity in the range of 2 to 2.5 % which is not acceptable for most of the customers.

The porosity should be less than 1%

Kindly suggest the factors which are affecting for higher porosity levels.


Regards,

SREENIVAS

Dear Sir
We strongly advise buyers of our equipment to pass the powder through a sieve, dry the powder before use and use a freezer to reduce moisture in the air.
90% of the quality of the coating depends on the quality of the powder.
Best Regards
A.Termika Ltd


Reply
05-23-2017, 06:46 PM,
#7
RE: Request for solution to reduce porosity in HVOF Tungsten Carbide Coatings
Hi Sreenivas

For me isn't clear what is your problem, is necessary to know the equipment, parameters and gun you are using, because surely there is something wrong in your equipment or parameters, With serious HVOF system and a good parameters set, you must have porosity under 1%, even with HVCW 1000 (HVOF wire), you can have porosity under 1%, so if you really need help with coatings, you must share parameters, and equipment, in order to have the correct solution to your problem, otherwise we are loosing time.
Best regards
Luigi
Reply
07-22-2020, 08:01 AM,
#8
RE: Request for solution to reduce porosity in HVOF Tungsten Carbide Coatings
Dear Sreenivas,

I am very late.
However I would like to share my knowledge for thermal spray.

The porosity, especially open pores are occured as some reason.
First one is size of powder, the bigger one has more porous coating layer and large open pores. Smaller powder has reduced porosity.
Second one is an absorption water molecular on surface of powder, especially agglomerated and sintered powder. It means powder drying method is not good during wet weather. Please check and compare the related moisture record for thermal sprayed work days.
And the other micro pores are related to a shadow effect by unmelted powder.

Wish your reduced porosity coating,

Simon
Reply




Possibly Related Threads…
Thread Author Replies Views Last Post
  Porosity problem - HVOF thaisrms 6 1,680 08-28-2020, 06:52 AM
Last Post: Vadim Verlotski
  Chromium carbide parameters for HVOF JP500 Jaryn 2 755 07-01-2020, 04:27 PM
Last Post: ap-praxair
  Tungsten Carbide HVOF Removal PrecisionCarbide 9 9,138 02-24-2020, 11:17 AM
Last Post: Packiaraj Mutharasu
  Hot Salt Bath Solution mmgerrie 10 2,731 07-29-2019, 06:11 PM
Last Post: Lemster68
Lightbulb Problem solved Grinding solution for Hastalloy HVOF coating plzc126330 3 2,422 05-28-2019, 01:08 PM
Last Post: velocity
  Twin Arc spray system ( request for your recommendation) demionkrishan 0 723 03-04-2019, 10:22 PM
Last Post: demionkrishan
  roller surface high roughness Tungsten carbide coating Ra 0.15-0.3mm zhuminkun 6 2,475 02-08-2019, 04:59 AM
Last Post: Taz
  Sharp edges on Hvof coatings velocity 1 1,155 06-25-2018, 03:49 PM
Last Post: Vadim Verlotski
  Dark surface after grinding of plasma tungsten carbide coating Lazha 1 2,146 05-31-2017, 12:07 PM
Last Post: loriolo
  HVAF tungsten carbide to replace hard chrome - Help??!!! Adamreis 2 2,462 02-20-2017, 11:04 PM
Last Post: Vig
  HVOF porosity sprayloud 4 3,933 11-28-2016, 02:27 PM
Last Post: MVagusta
  Effective Way of Testing hardness of Tungsten Carbide MANGESH 2 4,776 12-03-2015, 09:25 PM
Last Post: alaskangrown
  Tungsten Carbide coatings Sealants sorousheti 5 5,116 11-23-2015, 10:18 AM
Last Post: sorousheti
  Heat treatment after HVOF process to decrease porosity Giroud 3 4,489 07-13-2015, 05:51 AM
Last Post: aerotherm
  Cold Spray with Tungsten Carbide LLBHW 3 10,648 04-24-2015, 01:06 AM
Last Post: Fermit



Users browsing this thread: 1 Guest(s)





Surface Engineering Forum Sponsor - Alphatek Hyperformance Coatings Ltd