Each pass thickness & interpass temp. confused
02-22-2020, 07:55 AM, (This post was last modified: 02-22-2020, 08:06 AM by DMan.)
#21
RE: Each pass thickness & interpass temp. confused
Dear Vadim

First of all a big thanks to you from my end. Your suggestions and inputs have helped me to overcome my issues on aluminium base and now i am making a wonderful and neat and clean product.

I have a few more questions regarding Base materials.

I am getting some old base MS metals coated with tungsten carbide on which i am supposed to make a ceramic Cr2O3 coating.
I was able to remove the TC layer by grit blasting (very hard though ) to get a MS layer , but not sure if thats the correct way to do so since in a few weeks in printing the ceramic peeled off from the base.

Please guide me what should i do if in case i get copper-chromed/tungsten carbide coated MS bases and what has to be done to get a proper MS base after scrapping the same suitable for ceramic

With warm regards
DMan

Dear DMan,

You don't need preheating to apply bond coat. However, all parts should be warm before thermal spraying to avoid possible water condensation (general rule). It is enough 40-50°C to remove condensation.

Regards
Vadim
[/quote]

Reply
02-22-2020, 09:25 AM,
#22
RE: Each pass thickness & interpass temp. confused
Dear DMan,

almost all old coatings can be removed by sandblasting with corundum, but not the coatings of tungsten carbide, which are removed very slowly in this way. The removal of old coatings by means of shot-blasting with steel grit leads to hardening of the steel substrate, therefore, the adhesion of the new coating to the substrate may deteriorate.
To remove coatings from tungsten carbide, electrochemical etching in an alkaline solution (Rochelle salt) is successfully used. You can read about this method on the Internet, including on this forum.

Regards
Vadim
Reply
03-15-2020, 09:49 AM,
#23
RE: Each pass thickness & interpass temp. confused
Dear Vadim

A few more questions which have popped up in the last few weeks to enhance quality issues.

Right now I use Oerlicon Metco 6156 Top Coat for Ceramic coating for anilox.
A few suggestions have been to use small percentage of Titanium oxide in the same powder which comes as another powder for Top Coat.

Can you guide me the advantages of using Titanium Oxide along with Cr203 in the top coat which may help me to enhance my anilox quality and if at all it will be helpful.I hear few Anilox manufacturers around the world do the same so just wondering why.


Await to hear your feedback on the matter.
Warm Regards
DMan



Dear DMan,

You don't need preheating to apply bond coat. However, all parts should be warm before thermal spraying to avoid possible water condensation (general rule). It is enough 40-50°C to remove condensation.

Regards
Vadim
[/quote]

Reply
03-15-2020, 04:14 PM,
#24
RE: Each pass thickness & interpass temp. confused
Dear DMan,
the addition of titanium oxide to chromium oxide slightly reduces the melting point and improves the sintering of the material. It is difficult to say how much this affects the coating properties of anilox rolls.
I think that a greater influence on the quality of the coating is exerted not by the addition of titanium oxide to chromium powder, but by the quality of the powder for spraying. If you have a high-quality powder of pure chromium oxide (particles less than 25 microns + a narrow particle size distribution), then the coating will be better than with a low-quality powder Cr2O3 + TiO2.

Regards
Vadim
Reply
05-16-2020, 09:43 AM,
#25
RE: Each pass thickness & interpass temp. confused
Dear Vadim

Hope you and all others are doing well in these critical times of Covid.
Of recent i got a few feedbacks for our Anilox sleeves which is done on AL base.
Although the appearance of the sleeves are very good , in between we see some sort of minute air pockets which in later stages or during printing burst and give a spot effect on print.
I am attaching a picture. Can you help me with this issue.



Dont know if its the right URL..please confirm me.

Some points.

1.The top coating was done at 10 microns/layer
2.max Temp didnt go beyond 97 degrees during coating.
3.There is a 100 micron base coat and 200 micron Top coat.
4.I used a minimal blasting pressure of 2 bars to get a fine blast profile.

Please provide me some inputs so that I can improve on the present case.
Warm Regards
DMan



Dear Vadim

First of all a big thanks to you from my end. Your suggestions and inputs have helped me to overcome my issues on aluminium base and now i am making a wonderful and neat and clean product.

I have a few more questions regarding Base materials.

I am getting some old base MS metals coated with tungsten carbide on which i am supposed to make a ceramic Cr2O3 coating.
I was able to remove the TC layer by grit blasting (very hard though ) to get a MS layer , but not sure if thats the correct way to do so since in a few weeks in printing the ceramic peeled off from the base.

Please guide me what should i do if in case i get copper-chromed/tungsten carbide coated MS bases and what has to be done to get a proper MS base after scrapping the same suitable for ceramic

With warm regards
DMan

Dear DMan,

You don't need preheating to apply bond coat. However, all parts should be warm before thermal spraying to avoid possible water condensation (general rule). It is enough 40-50°C to remove condensation.

Regards
Vadim
[/quote]


[/quote]



Attached Files Thumbnail(s)
   
Reply
05-16-2020, 10:56 AM,
#26
RE: Each pass thickness & interpass temp. confused
Dear DMan,

The defects seen in the picture were caused by corrosion of the aluminum substrate. Since both layers (top coat and bond coat) are not waterproof, aluminum can corrode underneath and such white spots of aluminum hydroxide occur.
There is usually only one way to prevent substrate corrosion from anilox rollers: imprign with special organic sealants. You can buy such sealants, for example, from powder suppliers. I don't know which sealants are best suited for this task. I am not a sealant specialist and cannot help you here.

Regards
Vadim
Reply
05-24-2020, 10:56 AM,
#27
RE: Each pass thickness & interpass temp. confused
Dear Vadim

Thank you very much . Points noted and i am trying to implement the same.

I am a bit curious on one aspect of ceramic cr2o3 coatings.
What is the best way to remove an already coated ceramic (cr2o3) piece.
We use aluminium grit blasting ..but sometimes due to high ceramic layer thickness takes a lot of time to strip off the old ceramic. I always wonder if theres a way i can just strip some of the top 50 micron ceramic and coat a new layer saving me lots of time and powder wastage.

Await your feedback.

regards
DMan

Dear DMan,

The defects seen in the picture were caused by corrosion of the aluminum substrate. Since both layers (top coat and bond coat) are not waterproof, aluminum can corrode underneath and such white spots of aluminum hydroxide occur.
There is usually only one way to prevent substrate corrosion from anilox rollers: imprign with special organic sealants. You can buy such sealants, for example, from powder suppliers. I don't know which sealants are best suited for this task. I am not a sealant specialist and cannot help you here.

Regards
Vadim
[/quote]

Reply
05-25-2020, 06:14 AM,
#28
RE: Each pass thickness & interpass temp. confused
Dear DMan,
The best way to remove a ceramic coating is by sandblasting. In theory, you can also remove the Cr2O3 coating chemically (immerse the roller in acid) or thermally (warm the roller to 400-500°C), but the substrate surface will be damaged.
The sandblasting can be carried out very quickly and dust-free, you only need the powerful sandblasting system with a suction box.

Regards
Vadim
Reply
05-29-2020, 07:17 AM,
#29
Shy  RE: Each pass thickness & interpass temp. confused
Dear Vadim

Thanks for the reply.

2 questions as always Smile

a) I have Al grit blasting machine and usually remove ceramic with that.(waste lot of time)
Will AL grit blasting be ok or is Sandblasting the best way to remove ceramic?

b) If i have to recoat a MSroller/AL sleeve, should old coating be completely stripped off by blasting and then again coated or can i grind off some of top ceramic layer and recoat the same directly. I am just curious to know this. Never tried.


Await your feedback.

Regards
DMan

Dear DMan,
The best way to remove a ceramic coating is by sandblasting. In theory, you can also remove the Cr2O3 coating chemically (immerse the roller in acid) or thermally (warm the roller to 400-500°C), but the substrate surface will be damaged.
The sandblasting can be carried out very quickly and dust-free, you only need the powerful sandblasting system with a suction box.

Regards
Vadim
[/quote]

Reply
05-29-2020, 07:59 AM,
#30
RE: Each pass thickness & interpass temp. confused
Hi DMan,

I hope that under your "Al grit blasting" you understand sandblasting with corundum (Al2O3). White corundum grit 90 (EKF 90) would be best for your purposes.

For the new coating, the old layer must always be completely removed and the substrate surface must be freshly sandblasted. Coating on sanded remnants of the old layer will not work.

Regards
Vadim
Reply
05-29-2020, 09:44 AM,
#31
RE: Each pass thickness & interpass temp. confused
Dear Vadim

Thanks again .
It clears some of my misconceptions.
Warm regards
DMan


Hi DMan,

I hope that under your "Al grit blasting" you understand sandblasting with corundum (Al2O3). White corundum grit 90 (EKF 90) would be best for your purposes.

For the new coating, the old layer must always be completely removed and the substrate surface must be freshly sandblasted. Coating on sanded remnants of the old layer will not work.

Regards
Vadim
[/quote]

Reply
06-19-2020, 11:45 AM,
#32
RE: Each pass thickness & interpass temp. confused
Dear Vadim

One question as always.

Is there any way to fill up a Cr203 ceramic pinhole.
I mean sometimes after a full process (mostly after grinding ) , I lose a roller just because of a tiny little pin hole.

Any filling paste that I can apply to fill the same?

Await to hear you.
Warm regards
DMan

Dear Vadim

Thanks again .
It clears some of my misconceptions.
Warm regards
DMan


Hi DMan,

I hope that under your "Al grit blasting" you understand sandblasting with corundum (Al2O3). White corundum grit 90 (EKF 90) would be best for your purposes.

For the new coating, the old layer must always be completely removed and the substrate surface must be freshly sandblasted. Coating on sanded remnants of the old layer will not work.

Regards
Vadim
[/quote]


[/quote]

Reply
06-19-2020, 07:46 PM,
#33
RE: Each pass thickness & interpass temp. confused
Dear DMan,
You can’t make a full-fledged repair of such a defect, but you can make a cosmetic repair by filling in the defect with a homemade epoxy putty with chromium oxide powder (you must mix your spray powder in the epoxy glue).

Regards
Vadim
Reply
06-27-2020, 01:25 PM,
#34
RE: Each pass thickness & interpass temp. confused
Dear Vadim

I have been having the oxidation issue on Aluminium Base and quite often get the white powder development after grinding.

I have used the sealant from DIAMANT DICHTOL WFT 1532 but didn't have any luck on Aluminium.

Is there any other preventive measures I can take to stop the oxidation. What other factors can cause the same.(eg Humidity in room? Grinding Water Quality ?? etc )

When i leave the Aluminium sleeve overnight, the next morning i see the white bulge which sometimes opens up. It causes me a full rejection of the sleeve.

Await to hear you.
Warm regards
DMan
Dear Vadim

Hope you and all others are doing well in these critical times of Covid.
Of recent i got a few feedbacks for our Anilox sleeves which is done on AL base.
Although the appearance of the sleeves are very good , in between we see some sort of minute air pockets which in later stages or during printing burst and give a spot effect on print.
I am attaching a picture. Can you help me with this issue.



Dont know if its the right URL..please confirm me.

Some points.

1.The top coating was done at 10 microns/layer
2.max Temp didnt go beyond 97 degrees during coating.
3.There is a 100 micron base coat and 200 micron Top coat.
4.I used a minimal blasting pressure of 2 bars to get a fine blast profile.

Please provide me some inputs so that I can improve on the present case.
Warm Regards
DMan



Dear Vadim

First of all a big thanks to you from my end. Your suggestions and inputs have helped me to overcome my issues on aluminium base and now i am making a wonderful and neat and clean product.

I have a few more questions regarding Base materials.

I am getting some old base MS metals coated with tungsten carbide on which i am supposed to make a ceramic Cr2O3 coating.
I was able to remove the TC layer by grit blasting (very hard though ) to get a MS layer , but not sure if thats the correct way to do so since in a few weeks in printing the ceramic peeled off from the base.

Please guide me what should i do if in case i get copper-chromed/tungsten carbide coated MS bases and what has to be done to get a proper MS base after scrapping the same suitable for ceramic

With warm regards
DMan

Dear DMan,

You don't need preheating to apply bond coat. However, all parts should be warm before thermal spraying to avoid possible water condensation (general rule). It is enough 40-50°C to remove condensation.

Regards
Vadim
[/quote]


[/quote]


[/quote]

Reply
06-28-2020, 02:23 PM,
#35
RE: Each pass thickness & interpass temp. confused
Dear DMan

I have not worked with DIAMANT DICHTOL WFT 1532 myself, but this product must work for your layers. Maybe you're doing something wrong when using it? According to the specification, the part must be degreased well before the impregnation and be colder than 40°C (even when grinding, the temperature must not exceed 40°C). Do you pay attention to it? You must also pay attention to storage (below 20°C, dry) and shelf life (<5 years).
Reply
07-12-2020, 05:35 PM,
#36
RE: Each pass thickness & interpass temp. confused
Dear Vadim
I am following whatever steps you are suggesting. May be I will catch the issue soon.
One question.
What is the humidity factor of the powder coating room ideal for plasma coating of cr2o3.
Do we have to maintain the humidity in sand blasting room as well. At the moment we have humid condition due to change of season to rains.
How big the humidity level effects the rusting issue on MS and AL base

Await to hear you again
Warm regards
DMan
Reply
07-13-2020, 12:25 PM,
#37
RE: Each pass thickness & interpass temp. confused
(07-12-2020, 05:35 PM)DMan Wrote: Dear Vadim
I am following whatever steps you are suggesting. May be I will catch the issue soon.
One question.
What is the humidity factor of the powder coating room ideal for plasma coating of cr2o3.
Do we have to maintain the humidity in sand blasting room as well. At the moment we have humid condition due to change of season to rains.
How big the humidity level effects the rusting issue on MS and AL base

Await to hear you again
Warm regards
DMan


Dear DMan,

moisture can have a very large negative influence on thermal spraying, namely on both processes: sandblasting and coating. There is a simple rule: the lower the moisture, the better. If the air humidity is high, the water condenses on the component during sandblasting and causes corrosion and adhesion problems. The moist spray powder also poses problems because it tends to form lumps.

Of course, you cannot influence the weather and have to live with the humidity that is prevailing at the moment, but there are a few tricks to eliminate negative influences from the high humidity:

For sandblasting in a damp atmosphere, the part must be heated to 120-150°C before blasting. The component cools to 40-50°C during blasting, but at such temperatures there is still no condensation.
The wettable powder in powder feeder must also be 40-50°C warm so that it does not clump. You can warm it up in a drying cabinet before filling or buy a special heating manget for your powder feeder.

Regards
Vadim
Reply
07-15-2020, 07:10 PM,
#38
RE: Each pass thickness & interpass temp. confused
Dear Vadim
Thanks again.

Before blasting,For MS base it's ok...I will heat to 120 degrees...will the same preheat apply for AL base?

In Coating Room,in high humidity..should I preheat the blasted base again with the
plasma gun before bondcoat? May it help ?
Warm Regards


Reply
07-16-2020, 05:50 AM,
#39
RE: Each pass thickness & interpass temp. confused
(07-15-2020, 07:10 PM)DMan Wrote: Dear Vadim
Thanks again.

Before blasting,For MS base it's ok...I will heat to 120 degrees...will the same preheat apply for AL base?

In Coating Room,in high humidity..should I preheat the blasted base again with the
plasma gun before bondcoat? May it help ?
Warm Regards

Dear DMan,
preheating the component prevents condensation of the water from the moist air. In this sense, it is important that the component remains warm between sandblasting and coating. It would be ideal if you could keep the part in a warming cabinet all the time.
Of course, it also applies to aluminum parts.

Warm Regards
Vadim
Reply
07-19-2020, 10:45 AM,
#40
RE: Each pass thickness & interpass temp. confused
Dear Vadim

Thanks again for the advice.
Can you let me know something about Diamalloy 1003 /or 316 L from Metco and its application.
I hear its use in printing rollers but not sure how can it be used . A substitute for Bond Coat ? Will it help me in a humid atmosphere on MS ?

Best Regards
DMan
Dear Vadim
Thanks again.

Before blasting,For MS base it's ok...I will heat to 120 degrees...will the same preheat apply for AL base?

In Coating Room,in high humidity..should I preheat the blasted base again with the
plasma gun before bondcoat? May it help ?
Warm Regards



[/quote]

Dear DMan,
preheating the component prevents condensation of the water from the moist air. In this sense, it is important that the component remains warm between sandblasting and coating. It would be ideal if you could keep the part in a warming cabinet all the time.
Of course, it also applies to aluminum parts.

Warm Regards
Vadim
[/quote]

Reply




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