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Quote:Posted by John Beville(24.123.144.177) on 22:11:47 04/10/05

I have a hardness being reported in (HV 0.05)squared. What is this terminology and how does it correlate with HRC (asa guideline)?
The actual HV hardness is 3000.

Quote:Posted by ramchattopadhyay (202.177.180.140) on 07:40:0105/10/05

In Reply to: Vickers Hardness posted byJohn Beville

Maximum of HRC scale, i.e., 80 RC corresponds roughly to 800HV.
HV hardness above 800 HV is beyond HRC scale.
& there is no conversion possible from HV to HRC.
In my book on surface wear all the hardness scales are discussed along with a approx conversion scale.

Quote:Posted by John Beville(24.123.144.177) on 18:03:52 05/10/05
In Reply to: Re: Vickers Hardness posted by ram chattopadhyay

Dr. Chattopadhyay,
Can you please post the table of contents of your books?
Thank you

Quote:Posted by John Beville(24.123.144.177) on 15:20:09 05/10/05

In Reply to: Re: Vickers Hardness postedby ram chattopadhyay

Thank you.
I still need to know more about what the 0.05 squared means.I've seen the "HV/30" and "HV/10" terminology, but do not understand how one relates to the other, nor how the 0.05 squared relates to either of them.

Quote:Posted by Gordon England (62.252.0.12) on 18:52:13 05/10/05

In Reply to: Re: Vickers Hardness postedby John Beville

Hi John


Estimated Hardness Equivalents between Vickers and Rockwell C

I can only think that 0.05 stands for the load/force as in HV/0.05 meaning a 50g load was used.
Measuring hardness above 900/1000 HV using Rockwell C is not practical. Conversions are very much guesswork in this region as there is no way to verify the results.
Regards Gordon

Quote:Posted by ram chattopadhyay (202.177.151.92) on 10:22:03 16/10/05

In Reply to: Re: Vickers Hardness postedby John Beville

HV 0.05 is microhardness value of a hard phase or material at a load of 0.05 gram. Microhardness testing is used for high hardness thin coatings. Load to be used decreases with thinner coating so as to ensure non-penetration of indentor in the substrate material.
ram
P.S please send a mail at drrammandira@yahoo.com in order to enable reply to enquiries on books' content list. my other account has become non-operative.

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Quote:Posted by becky (132.244.246.24) on 11:49:59 25/05/06

Hello.
When spraying APS coatings, which paramters do you all consider to be the most important variables that need to be monitored for the purposes of statisical process control?
Any help much appreciated.
Becky.

Quote:Posted by Gordon England (62.252.0.12) on 01:02:42 02/06/06

In Reply to: key process variables for APS posted by becky

Hi Becky
Not too sure what you mean by statisical process control, but I would say all the process parameters need to be monitored.
Regards Gordon

* https://www.gordonengland.co.uk/tsc.htm#Factors

Quote:Posted by becky (132.244.246.24) on 09:57:52 02/06/06

In Reply to: Re: key process variables for APS posted by Gordon England

Thanks for the response Gordon.
I would like to understand how SPC could be used to controlling the process. By utilising run charts to assess performance, it should be possible to identify potential problems before they become problems and enable you to avert a non-conforming coating before it is too late. Just as an example ~ wear on nozzles. How often should nozzles be changed? How can you monitor their wear such that they are replaced before they degrade and start affecting / contaminating a coating? What techniques do people use to detect wear etc etc. In a shop floor environment, not all factors can be watched by an operator, (maybe possible in a lab environment) so if only three (for the sake of argument) can be monitored, what three 'key process variables' would be best to monitor.
Any help from anyone greatly received.

Quote:Posted by Gordon England (62.252.0.12) on 21:49:22 02/06/06

In Reply to: Re: key process variables for APS posted by becky

Hi Becky
I would first choose voltage readings. On most modern constant current power supplies, voltage is dictated by the resistance of the plasma gases and nozzle/electrode geometry. Voltage is not normally a set parameter (assuming plasma gas flows are the primary setting). Voltage readings straying from normal range will indicate problems (nozzle/electrode wear, water/gas leaks, plasma gas flow problems).
Next would be powder feed rate and then gas flow rates (including carrier gas).
Best regards Gordon

Quote:Posted by becky (132.244.246.24) on 10:26:29 06/06/06

In Reply to: Re: key process variables for APS posted by Gordon England

Thank you Gordon, that is very helpful.
If the 'set' voltage is recorded on a run chart and then actual voltages are recorded, we should be able to ascertain if the process is starting to shift. This will be an interseting excercise.
Should the peak voltage during the cycle be measured, or at a particular time / times / point in the process? What do you think?
I'll also start taking the other readings that you have suggested and see if we can refine our process. Your help is very much apprecaited.
Kind regards
Becky.

Quote:Posted by Gordon England (62.252.0.12) on 14:20:52 06/06/06

In Reply to: Re: key process variables for APS posted by becky

Hi Becky
Monitoring voltage alone with no reference to other parameter settings would probably be a waste of time. Assuming you are monitoring a spray system where all settable parameters are kept constant (you spray same coating all the time)then monitoring voltage over time for any individual nozzle/electrode hardware set-up would be useful. It is important that you are able to relate voltage with the other parameter settings particularly plasma gas flows, current, etc. and hardware.
An interesting point is that a few set voltage to a specific point and keep this constant, so that they always maintain a constant power output. In this case plasma gas make-up and flow become the variable.
Hope this helps.
Regards Gordon

Quote:Posted by Wojciech (62.233.197.106) on 09:21:40 12/06/06

In Reply to:Re: key process variables for APS posted by Gordon England

Hi,
I was working on a plasma spraying symulation software, and on the process analising. We were interested in influence of variable process parameters on coatings properties.
We assumed that most important variables are:
- Power
- Torch-substrate distance
- Powder feed rate
- Carrier gas flow
Other important parameters I think would be:
- Torch scan speed
- Plasma gas composition
(- Point of powder injection - Angle of powder injection)
You might find interesting that the experiments were planned/analised using 'full factorial design'.
Regards,
Wojciech

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