01-10-2018, 08:34 PM,
(This post was last modified: 01-10-2018, 09:11 PM by Carguy1968.)
|
|
Carguy1968
Member
|
Posts: 5
Threads: 3
Joined: Jan 2018
Reputation:
0
| |
HVOF Grit Embeddment Help!
Hello All!
This is my first time posting, but have read many of the forums. I am reaching out to you to engage everyone’s opinion on a defect I am currently experiencing.
First off, we are spraying cylindrical parts using HVOF. Some are sprayed with a tungsten carbide blend, others are an iron blend. Nonetheless both materials are producing the same defect.
The defect occurs after grit blasting and HVOF spraying a workpiece. The coating produced has a series of small bumps in it. After some investigation it was concluded that these bumps were actually pieces of grit being coated over. After gritblasting the work pieces undergo a blow off process with compressed air. During finishing of the coating, i.e. grinding, these pieces would fall out causing small voids. These voids were confirmed with non destructive testing.
It appears odd because one day it was fine and the next this issue appeared. Grit supplier and all parameters are the same including no changes in workpiece material. Does anyone know what may be causing this embedment or steps to correct such?
Thanks much in advance!
-C
|
|
01-11-2018, 11:51 AM,
(This post was last modified: 01-11-2018, 11:58 AM by Vadim Verlotski.)
|
|
RE: HVOF Grit Embeddment Help!
(01-10-2018, 08:34 PM)Carguy1968 Wrote: Hello All!
This is my first time posting, but have read many of the forums. I am reaching out to you to engage everyone’s opinion on a defect I am currently experiencing.
First off, we are spraying cylindrical parts using HVOF. Some are sprayed with a tungsten carbide blend, others are an iron blend. Nonetheless both materials are producing the same defect.
The defect occurs after grit blasting and HVOF spraying a workpiece. The coating produced has a series of small bumps in it. After some investigation it was concluded that these bumps were actually pieces of grit being coated over. After gritblasting the work pieces undergo a blow off process with compressed air. During finishing of the coating, i.e. grinding, these pieces would fall out causing small voids. These voids were confirmed with non destructive testing.
It appears odd because one day it was fine and the next this issue appeared. Grit supplier and all parameters are the same including no changes in workpiece material. Does anyone know what may be causing this embedment or steps to correct such?
Thanks much in advance!
-C
It can have many causes. We need images of the defect and microscopy of the cross-section to this place to say more. Maybe just the filter of grit blaster was not changed too long.
|
|
01-16-2018, 07:57 AM,
|
|
syam
Junior Member
|
Posts: 2
Threads: 0
Joined: Jan 2018
Reputation:
0
| |
RE: HVOF Grit Embeddment Help!
What is the exact surface profile requirement for HVOF process. Can anyone provide the ASME standards or is it based on the Metal powder specification.
Also anything regarding this is mentioned in ASME B-46.1.
Regards
SG
|
|
01-17-2018, 08:50 AM,
|
|
syam
Junior Member
|
Posts: 2
Threads: 0
Joined: Jan 2018
Reputation:
0
| |
RE: HVOF Grit Embeddment Help!
(01-17-2018, 01:15 AM)Taz Wrote: Hi Carguy,
What type of grit blasting that you use?
What are the grit blast size are you using?
we are using aluminum oxide grit
|
|
|