Surface preparation and its effect on fatigue life and bond strength
06-11-2010, 06:19 PM,
#1
Surface preparation and its effect on fatigue life and bond strength
We are involved in the repair of bearing surfaces on large rotating shafting subjected to reverse bending stress. We have a customer that is extremely concerned about the fatigue life of their equipment. The concern is that grit blasting the bearing surface prior to metallzing will adversely effect the fatigue life of the shaft. Does anyone know of a proven, adequate surface prepation method that can be used under a twin wire arc or HVOF coating? We are looking for a balance between enhancing fatigue life properties and the bond strength of the coating. Or is there any information available about the effects of a different metallized coatings on the fatigue strength of the part?
Reply
06-23-2010, 04:39 PM,
#2
RE: Surface preparation and its effect on fatigue life and bond strength
Hi WMW

Sign0016 to the Surface Engineering Forum.

Sorry for late response, I think your thread was over looked because you placed it in the wrong forum section. I will move it to surface engineering, where hopefully it should gain more attention.

I can only respond to question somewhat generically in saying thermal spray coatings are said to have little effect on fatigue strength in themselves. Grit blast preparation is said to give a slightly negative effect fatigue strength. I think it may be dangerous to take generalisations and apply to specific applications and conditions. I have seen a number of papers on the subject over the years, some conflicting, but I think this down specific conditions of materials, processing and testing.

I have come across heavy shot peening of surfaces prior to light grit blasting, supposedly to compensate for fatigue loss effects of grit blasting.

Is there a history of fatigue failure with this component or is your customer being overly concerned?
Reply
06-24-2010, 07:17 AM, (This post was last modified: 06-24-2010, 07:20 AM by Viking.)
#3
RE: Surface preparation and its effect on fatigue life and bond strength
(06-11-2010, 06:19 PM)WMW Wrote: We are involved in the repair of bearing surfaces on large rotating shafting subjected to reverse bending stress. We have a customer that is extremely concerned about the fatigue life of their equipment. The concern is that grit blasting the bearing surface prior to metallzing will adversely effect the fatigue life of the shaft.
This responce based entirely on observation (over decades),
and has no educated basis.

I have been suspisious for years of grit-balsting not necessarily always
being the best prep for a number of build-up tecniques.

Once I got involved in tigging my own repair build-ups
on tool-steels, I noticed that some blasting of some regions
on some tools gives poor wetting, or blocks it entirely in corners
and tight regions as I try to get the corners to collapse and
receive filler.

I did some test blasts at angles from very near paralell to
the tig-target area, to perpendicular.
Also nozzel up close to far off.
When tigging blasted regions where close nozzle or perpendicular
or both were used, I'm convinced that blast media has been
imbedded into the tool-steel.

This could interfere with any bond no?.
But as for fatigue.......on large shafting,
professional (uneducated) "opinion" is
very unlikely. I have seen all manner of failures.
And nothing to suggest or support that concern.
Viking.
Reply
06-28-2010, 03:35 PM,
#4
RE: Surface preparation and its effect on fatigue life and bond strength
Hi WMW and Viking

Quote:I have been suspisious for years of grit-balsting not necessarily always
being the best prep for a number of build-up tecniques.

Quote:When tigging blasted regions where close nozzle or perpendicular
or both were used, I'm convinced that blast media has been
imbedded into the tool-steel.

This could interfere with any bond no?.

From the point of view of thermal spray coatings and no doubt other coating processes that predominantly rely on mechanical keying for bonding, grit blasting is extremely important. Processes involving metallurgical bonding such as welding could be very different though.
Reply
06-29-2010, 08:41 AM,
#5
RE: Surface preparation and its effect on fatigue life and bond strength
Hi,
The grit blasting supposed to produce compressive residual stress on the surface of the component.Hence grit blasting as such should improve the fatigue life to an extent depending on the quantum of residual stress generated.Hence I believe that there should not be any loss of fatigue strength by grit blasting.
ram chattopadhyay
Reply




Possibly Related Threads…
Thread Author Replies Views Last Post
  Substrate preparation VS bonding strength plzc126330 2 1,694 01-09-2018, 03:48 AM
Last Post: plzc126330
  Info needed on Bond Strength for Thermal Spray powders hereticgame 1 1,860 10-10-2017, 11:39 AM
Last Post: Vadim Verlotski
  Silicon and Hafnium coating powder effect achmadarifudinh 1 1,395 08-23-2017, 01:39 PM
Last Post: mgbaca1
  Good preparation for cast iron base material plzc126330 3 2,163 11-24-2016, 01:17 AM
Last Post: plzc126330
  95Ni 5Al bond strength alaskangrown 1 2,357 01-15-2016, 05:09 PM
Last Post: loriolo
  Surface Preparation of Aluminium acidic 2 3,225 05-09-2015, 01:59 PM
Last Post: CHI3
  HVOF T800 Tensile Bond Strength issue wgg237 2 3,794 03-05-2015, 01:52 AM
Last Post: wgg237
Shocked Hard Crome Plating Bond strength Met.Eng. 4 5,454 02-24-2015, 02:37 AM
Last Post: Simon Kim
  Arc Wire Spraying Bond Strength wtaz 4 4,372 12-04-2014, 12:02 AM
Last Post: wtaz
  Life of JP 5000 Gun Parts? RV_DMG 5 5,146 11-14-2014, 03:33 PM
Last Post: hvofhamid
  Abradable Coating-Bond Strength rayudugirish 9 11,201 01-06-2014, 09:55 PM
Last Post: derek
  Effect of weather on deposition efficiency Max K 3 3,832 08-06-2013, 04:40 PM
Last Post: GMA thermal spray systems
  what's the effect of the spray energy to the coating's hardness? Spark 3 4,083 07-10-2013, 05:55 PM
Last Post: loriolo
Information Chrome oxide thermal sprayed coatings shelf life Leanne 1 3,064 02-14-2013, 02:18 PM
Last Post: Gordon
  HVOF Barrel Life Span sreenuvundela 4 5,072 11-10-2012, 11:33 AM
Last Post: Rohit Upadhyaya



Users browsing this thread: 1 Guest(s)





Surface Engineering Forum Sponsor - Alphatek Hyperformance Coatings Ltd