Mo wire spraying
09-01-2017, 09:06 AM,
#1
Mo wire spraying
Hello,

I need advice about spraying of Mo wire (D1,6mm) in order to avoid any possible mistakes during spraying. The cylinder internal surface we will spray is over 1000mm. Weight over 5 tons. Base material 0,4C carbon steel , hardness 200HB. Now surface is machined by grinding. Any information who has experience will be important from preparing of the surface, preheating, spraying, thickness per pass, minimal linear speed, temperatures, machining..... what minimal and maximum thickness of Mo coating can be after final machining?

Best regards
Arturas
Reply
09-04-2017, 06:04 AM,
#2
RE: Mo wire spraying
Hi Arturas

You forgot the most important think, necessary in order to answer your question, what kind of system do you are going to use, Arc spray, Flame spray,HVOFW, and specifications about bonding, roughness, hardness
Best regards
Luigi
Reply
09-04-2017, 07:35 AM,
#3
RE: Mo wire spraying
Hi,
We will use HVOF wire system -HiJet 9610.
Final coating surface roughness Ra0,3, hardness 1100 HV0,05
Best Regards
Arturas

(09-04-2017, 06:04 AM)loriolo Wrote: Hi Arturas

You forgot the most important think, necessary in order to answer your question, what kind of system do you are going to use, Arc spray, Flame spray,HVOFW, and specifications about bonding, roughness, hardness

Reply
09-05-2017, 04:35 PM,
#4
RE: Mo wire spraying
Hi Arturas

I had some experience with the system HVOW HiJet 9660, and it works very well and the molibdenum coating I did was on car sinchonizer ring, and there was a very good bond, low roughnes (quite like Standard HVOF) and very low porosity, we applied about 0,4 mm without problems, and the temperature during spray was about 180 °C, I think there is no problem with temperature of the part, just preheat in order to evitate condensation, but an important think is to clean very well surfaces, and , the preferred abrasive for almost thermal spray applications would be Al2O3. Different mesh sizes of this grit under varied air pressures is used in order to obtain differents profiles. Typically for HVOF coatings, a 80 grade size aluminum oxide using 5 kg/cm2 air pressure should give a surface Ra value of 12-15 microns, about hardness, as you know on moly coatings can be corrected with O2 parameters

Rotation speed (RPM) ≈ 75 ÷ (3,14x2r)
Periferical speed (m/min) (≥ 75 )
Translation speed (steps)(mm/rev) (≈ 4 )
Translation speed (m/min) ≥ 7,62
Coating thickness per pass [µm] ≤ 2 - 4
Best regards
Luigi
Reply
09-06-2017, 11:04 AM,
#5
RE: Mo wire spraying
Hello,
Thanks a lot for the information. I sprayed some samples. Quality is OK but there are problems with hardness. I tried different air pressure and notice that at 6,5atm of air coating hardness only about 30HRC when air 5atm coating hardness 40HRC. As I understand from you reply I should increase oxygen pressure ,flow ..... in order to increase hardness...What about wire feed?

Arturas

(09-05-2017, 04:35 PM)loriolo Wrote: Hi Arturas

I had some experience with the system HVOW HiJet 9660, and it works very well and the molibdenum coating I did was on car sinchonizer ring, and there was a very good bond, low roughnes (quite like Standard HVOF) and very low porosity, we applied about 0,4 mm without problems, and the temperature during spray was about 180 °C, I think there is no problem with temperature of the part, just preheat in order to evitate condensation, but an important think is to clean very well surfaces, and , the preferred abrasive for almost thermal spray applications would be Al2O3. Different mesh sizes of this grit under varied air pressures is used in order to obtain differents profiles. Typically for HVOF coatings, a 80 grade size aluminum oxide using 5 kg/cm2 air pressure should give a surface Ra value of 12-15 microns, about hardness, as you know on moly coatings can be corrected with O2 parameters

Rotation speed (RPM) ≈ 75 ÷ (3,14x2r)
Periferical speed (m/min) (≥ 75 )
Translation speed (steps)(mm/rev) (≈ 4 )
Translation speed (m/min) ≥ 7,62
Coating thickness per pass [µm] ≤ 2 - 4

Reply
09-07-2017, 12:17 PM,
#6
RE: Mo wire spraying
Hi Arturas

Wire feed must be regulated looking at the front od the wire, Mo wire must be like a needdle, and spray distance could be 100 mm, macro-hardness could be about 40/56 HRc, but you must measure the micro-hardness, and encreasing O2 pressure and flow, you can have about 630/ 700 Hv
Best regards
Luigi
Reply
09-15-2017, 01:29 PM,
#7
RE: Mo wire spraying
Hi,
Many thanks for the information. After the final grinding coating quality looks ok!!

Arturas

(09-07-2017, 12:17 PM)loriolo Wrote: Hi Arturas

Wire feed must be regulated looking at the front od the wire, Mo wire must be like a needdle, and spray distance could be 100 mm, macro-hardness could be about 40/56 HRc, but you must measure the micro-hardness, and encreasing O2 pressure and flow, you can have about 630/ 700 Hv

Reply




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