what's the effect of the spray energy to the coating's hardness?

[Spark]

hey,guys:
Q1:Could anybody explain to me the relationship between the energy and the coating'hardness?
Q2:We use sulzer metco spray system F4mb gun to spray coating.
in the parameter setting panel,we can set the parameter as a constant power or constant current way to control the energy supply. I'm confusing about these two methods.what is the different between these?
Q3:We spray metco 101bNS coating and we use sulzer's starting parameter.the results of the vickers hardness is not steady,sometimes it can reach 700HV 0.3 but sometimes just 600HV0.3, micro-cut and bond test is ok,
please give me some suggestions to solve the problem.
Many thanks.
best wish.
Spark.

[Gordon]

Hi Spark

Q1:Could anybody explain to me the relationship between the energy and the coating'hardness?

A very distant one, many factors in between. A low energy system can very often produce a good coating just as well as a high energy system. The major factors are particle temperature and velocity which have a closer relationship regarding the density and strength of a coating and thus the coatings "macro" hardness. The coating material will generally dictate the inherent particle hardness.

Q2:We use sulzer metco spray system F4mb gun to spray coating.
in the parameter setting panel,we can set the parameter as a constant power or constant current way to control the energy supply. I'm confusing about these two methods.what is the different between these?

Constant current is where the system maintains control over the the desired current setting and the voltage of the system is dependent on plasma gas flows. Variations in these flows, gas mixes and hardware condition will change the voltage and thus the power output.

Constant power is where the system maintains the power output by balancing the relationship between current and voltage. Not sure if your system changes current or gas flows to maintain a constant power output.

Q3:We spray metco 101bNS coating and we use sulzer's starting parameter.the results of the vickers hardness is not steady,sometimes it can reach 700HV 0.3 but sometimes just 600HV0.3, micro-cut and bond test is ok,
please give me some suggestions to solve the problem.

It is normal to have quite a wide spread of HV/0.3 hardness readings. What is your average hardness over 10 tests. Remember these coatings are quite heterogeneous in structure, you only need to hit a porosity site to get a low reading. If your average hardness is low, look at the metallography, chances are you will need to make the coating denser to increase average hardness. To make parameter changes to achieve this will involve manipulating particle temperature and velocity, it is not as simple as just changing energy or power output.

[Spark]

Hi,gordon.
thank you for your honest reply.

Constant current is where the system maintains control over the the desired current setting and the voltage of the system is dependent on plasma gas flows. Variations in these flows, gas mixes and hardware condition will change the voltage and thus the power output.
Constant power is where the system maintains the power output by balancing the relationship between current and voltage. Not sure if your system changes current or gas flows to maintain a constant power output.

As my experience, when we use the constant current recipe, the voltage will goes down as the electrode wear day by day. That means the power output is lower than the day when electrode is good.
So if you use constant current recipe, you may get different power output and thus different condition of the coating (may be not obviously). I doubt if it may bring some bad effects to my 101ns coating.
Which control way do you recommend in the recipe usually?

[loriolo]

Hi
The best is to use constant volt, and the system increase Hydrogen if necessary, in order to mintain plasma temperature constant, but take in main that the next start, maybe after you change nozzle, you must check for the correct setting of hydrogen, because you must have the last value in memory.