Appling The WC hard coating on Hard substrate
04-23-2015, 03:14 PM, (This post was last modified: 04-23-2015, 03:55 PM by behzadsaberi.)
#1
Appling The WC hard coating on Hard substrate
Hello sorry for my poor English
I recently have applied WC-17Co & WC-10Co-4Cr on hardened SPK substrates by HP-HVOF method, but during finishing stage the coats showed a lot of fine cracks and even delaminating. What are the reasons of??/
thanks for your recommendations.
Reply
04-23-2015, 05:39 PM,
#2
RE: Appling The WC hard coating on Hard substrate
(04-23-2015, 03:14 PM)behzadsaberi Wrote: Hello sorry for my poor English
I recently have applied WC-17Co & WC-10Co-4Cr on hardened SPK substrates by HP-HVOF method, but during finishing stage the coats showed a lot of fine cracks and even delaminating. What are the reasons of??/
thanks for your recommendations.

Hi behzadsaberi,

There may be two reasons for the formation of cracks in the coat (individually or both):
1. Overheating of the substrate during the spraying (> 200°C),
2. Too thick monolayer (layer in a single pass > 10 micrometers ).

If the part is small or have thin wall, then it is very easy to overheat. In this case, it is necessary to use a powerful cooling and reduce the spraying time (sprayed with breaks for cooling).
If the monolayers are too thick, you must increase the speed of the device with respect to parts (to increase the number of tour per minute).
Reply
04-23-2015, 06:30 PM, (This post was last modified: 04-23-2015, 06:31 PM by behzadsaberi.)
#3
RE: Appling The WC hard coating on Hard substrate
(04-23-2015, 05:39 PM)Vadim Verlotski Wrote:
(04-23-2015, 03:14 PM)behzadsaberi Wrote: Hello sorry for my poor English
I recently have applied WC-17Co & WC-10Co-4Cr on hardened SPK substrates by HP-HVOF method, but during finishing stage the coats showed a lot of fine cracks and even delaminating. What are the reasons of??/
thanks for your recommendations.

Hi behzadsaberi,

There may be two reasons for the formation of cracks in the coat (individually or both):
1. Overheating of the substrate during the spraying (> 200°C),
2. Too thick monolayer (layer in a single pass > 10 micrometers ).

If the part is small or have thin wall, then it is very easy to overheat. In this case, it is necessary to use a powerful cooling and reduce the spraying time (sprayed with breaks for cooling).
If the monolayers are too thick, you must increase the speed of the device with respect to parts (to increase the number of tour per minute).

Hi Vadim Verlotski
Thanks for your response
There are several notifications that i have to mention sooner:
1) two of the piece works that had been coated were capstan with about 290mm diameter and the rotation speeds were about 120 & 240 RPM respectively. Transverse speed was 10mm/s.
2) Temperature of all piece works were controlled during the spraying process and the Temperature never got above 150 degree.
3) Surfaces of the substrates were sandblasted and not greasy at all.
Vadim Verlotski your statements are totally true but I really suspect to material properties of the substrates, as I mentioned the own substrate was very hard (hardened SPK) before coating. So could the cause of the cracks and delaminating of the WC coat back to the material properties of the substrate Or any other factors that I have missed? if yes what could i do to resolve that.
thanks again for your Patience.
Reply
04-24-2015, 06:04 AM,
#4
RE: Appling The WC hard coating on Hard substrate
Hi behzadsaberi,
Hard material should not be a problem. The only difference is that the roughness after blasting possibly too low. After my feeling you have low transverse speed with too slow rotation speed. I would have taken a minimum of 500 RPM with a transverse speed of 30 mm/s.
Regards
Reply




Possibly Related Threads…
Thread Author Replies Views Last Post
  Sand Blasting with SiC or Hard Alloy Met.Eng. 0 644 03-07-2020, 07:13 PM
Last Post: Met.Eng.
  HVAF tungsten carbide to replace hard chrome - Help??!!! Adamreis 2 2,459 02-20-2017, 11:04 PM
Last Post: Vig
  replacing hard chrome coating on piston grisen 3 3,436 10-08-2015, 12:07 PM
Last Post: Guner
  THermal Spray and Hard Crome Coating Met.Eng. 4 3,889 07-11-2015, 03:40 PM
Last Post: Met.Eng.
  Coating for Epoxy substrate webrits 2 2,864 03-20-2015, 03:09 PM
Last Post: Laurent
  plasma hard masking vendors CHI3 2 4,104 03-16-2015, 03:20 AM
Last Post: Meeker77
  Thermal Barrier Coating Aluminum Substrate for corrosion resistance alaskangrown 4 4,909 03-02-2015, 06:43 PM
Last Post: alaskangrown
Shocked Hard Crome Plating Bond strength Met.Eng. 4 5,595 02-24-2015, 02:37 AM
Last Post: Simon Kim
  Hard coating on valve Edson 3 3,423 02-19-2015, 03:18 AM
Last Post: Axis Machine
  Hard Chrome failure on Ducati rocker arms!! Ago37 2 4,829 09-06-2014, 09:33 AM
Last Post: Stephen Booth
  substrate deformation of WC coating in gate valve ehsan 2 4,809 12-14-2010, 09:15 AM
Last Post: Asiaf
  Spraying on Magnesium substrate Madila Awalini 9 7,133 07-05-2010, 04:01 AM
Last Post: Madila Awalini
  Removing TCC coating from INC625 substrate mightyatom 1 5,759 10-01-2008, 09:41 PM
Last Post: Gordon
Question Is WC based hard coating is repairable? dibyendudhara 2 4,946 05-17-2008, 10:47 AM
Last Post: hvofhamid
  hard AlSi-graphite abradable coating fhyuan 5 11,077 07-18-2007, 09:28 PM
Last Post: Gordon



Users browsing this thread: 1 Guest(s)





Surface Engineering Forum Sponsor - Alphatek Hyperformance Coatings Ltd