Hello,
I have serious problem, how to make that WC/Co/4%Cr coating sprayed by HVOF (MicroJet system) on plunger (max pressure 200bar, work in pair with bronze hub) could work. After one month of working coating in some places go off. And in one place coating is??as a bubble with several small gaps.??I am attaching pictures with defects . Can anybody to explain it.
Substrate is steel X45Cr13 (DIN 17230-80). Thermal treatment : normalization
Coating thickness was 0.3mm on side after spraying and 0.1-0.15mm after grinding. After spraying??surface was painted with thick sealer layer (that moment temperature of coating was 20C).


How to attach pictures
Best regards
Arturas

Hello everyone!

What kind of coating is usually recommended for aluminium surfaces of shallow depth underwater vehicles? What sealant would you recommend?

Would it be possible to let me know of any companies which may the sealant?

Thanks in advance

Hi, this small company has given me a very good quote for PTFE coatings. I was wondering if anyone has heard of them, please let me know what you think of them. http://www.surface-engineering.co.uk

Hi All,

This is a question pertaining the control of thermal spraying process. I hope someone who is in this line would be able to help to feed me with some info on different standard of practices in different shops around the globe.

What would be the maximum Machine hold-up period or time allowed between 2 spraying operation with the powder recipe/paramter, machine set-up be it in hardware or software conditions unchanged?

Assume that the previous spraying operation has a specimen attached to the part and the specimen has passed all QA test and criteria. And for continuous spraying operation, we need only one specimen to be representative of all the parts we spray in continuos mode. e.g: 1 specimen represents 8 parts sprayed in a day in continous motion. Once specimen has passed, all the part will be proceeded with post treatment or shipped, else a rework for all the parts will be disposed.

Yet, if I have finished all the parts, at 10:00a.m, without tearing down the gun or changing any thing, I have a part that comes in at 4p.m. There is a gap of 6 hours here. Do I need to spray the part with another specimen again? or I can take the advantage of the previous specimen result to continue to spray this part. If the answer is yes, then , again my question is how long maximum gap (in hours) is allowed or recommended, 6 hrs? 8 hrs? 12 hrs or without 24 hrs?

Thanks.

Regards,
Alex

I have 2 surfaces of Stainless Steel (316) at high temperature ~600C in vacuum and under a high pressure. These surfaces need to release from each other after the pressure is removed and the tempeture reduced. They stick together, I believe by diffusion welding. Elsewhere in the design HVOF Alumina has been applied successfully (at 800C). However this is a very expensive process, is there any alternative that might be used eg Wet Hydrogen Heat Treatment to form thicker Chrome Oxide layer to reduce this effect.

Nick

Hi,
I see that such problems are not typically discussed in the forum but I hope somebody can help me. As university researcher I work with an old (1991) Plasma Technik M500T plasma spraying system. Better to say I would work if it were working
The troubles began when the powder feeder did not started but the plasma was ready. Nevertheless I was able to spray with a simple gravitation feeder which I get from a simple combustion gun.
Since then an other problem has arisen: the automatic starting process stops at the third step and the plasma flame doesn't forms. (for appreciatives: X117 input is inactive.) This means that the current reaches only appr. 170A and the voltage is 80V instead of the operating 68V, Argon is flowing.
I would greatly appreciate any useful advice to solve the failure(s) before we would be forced to call a technician from Sulzer Metco for on-site repair. Thank you!

P?ter

Gordon,

I have a question pertianing the matter above, as you know the electrode that we use in for the air plasma e.g: for 9MB contains Thrioated Tungsten.

I have got a few paper produced by The National Radiological Protection Board in England that talk in detail about the material. But I do not know how to attach them to you. (Let me know if you are interested).

This paper appears to be addressed primarily to the welding industry, which I know little about but it suggests that grinding of thoriated tungsten is practiced. The paper makes clear that thoria is radioactive and states that internal exposure is likely to exist during grinding. In addition to the risk of inhalation, it further states that dust arising from grinding can settle on surfaces and contaminate body and clothing. As you know, the electrodes that we use contain thoriated tungsten and this can be hazardous to the health of workers (You may also note that, without any grinding, there exists a very low exposure to external radiation from our electrodes but this amount is considered negligible).

The reason for the regrinding which I have tested is an initiative of lean event to reduce hardware cost. We manage to salvage atleast >50% consumption of electrodes in an annual basis without affecting any quality of the spraying and coating integrity which I have verified. An electrode can be salvaged max 2 times before it is scrapped.

This is more on sharing and to seek your advice on this practice if this is advisable to continue by putting all the safety measurement in place to eliminate the risk? and if the safty measure is verified by a professional team of EH&S personnel after their have reviewed them.

What 's your opinion on this?

Regards,
Alex

Gordon,

I have a question on the tolerance capability level for thermal spray processes
.
I would like to know, what is the best tolerance (i.e. +/- 0.00x) that can be achieved with HVOF or Air Plasma?

For my process
1. APS - I could achieve a deposition rate in the range of 0.001"~0.003" per pass.

2. HVOF - I could achieve a deposition rate in the range of 0.00025 ~0.0005

Any information would be appreciated!

Thanks.

Regards,
Alex

From where can I buy small quantities of powdered carbon steel in the uk?

Dear Members
We have to sell 200 kgs AlCro, dia. 1.6 mm arc-spray wire.
Please contacts us.
Regards Kalmar