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Hello Colleagues, In advance of a thermal spray coating process, a sand blasting with abrasive grit material (e.g. corrundium) is required to reach a sufficient bonding strength of the coating. The grit blasting process leads to embedding of grit into the substrate as well as to small...

OK, I agree. Thank you for the beneficial hint!

Thank you, thats the same what our chemist (and the ASTM) says! But I only want to understand it - what could cause the problems here? Thanks and best regards Feldmann

Hello! Does anybody know if it would help to use a single crystal alloy if I have problems with wet intergranular corrosion? No grain boundaries, no chromium depletion at the grain, no possible attack? Or is it not as simple as I am thinking? Thanks for your comments in advance! Feldmann

I am planning a comparative testing campaign of various Ni/Co/Fe superalloys designated to be uses in a combustion chamber (wall temperatures 1500°F, gases: H2O vapour, CO, NOx, CO2, NHx, H2). The combustion chamber has a service life of approx 100h. I have at the moment approx. 20 different...

Thanks metengr; Of course, I have to perform at least two corrosion test campaigns, because I have in field service wet intergranular as well as hot corrosion attack. I wanted to start with the wet integranular case because there are standards and the test is relatively easy and affordable.

Thanks for your comment, our standard procedure before welding is ultrasonic cleaning in degreasing agent. Do you know if superalloys form scales (alumina oxide or chromium oxide) which are not visible for the naked eye and that are anyway detrimental with regard to welding performance? Or is is...

Dear Colleagues, Do you know if it is beneficial for the welding result to remove scales from superalloys prior to EB welding? We have many years experience with alloy 75 EB welding. After mechanical machining, in some cases there is a time duration of several weeks (storage under ambient...

Dear Colleagues, I am planning a series of Huey Tests with different materials, each material (a piece of tube) with two different heat treatments (EB welding and oven treatment for 5h at 1500°F). So according to the standard, it is not allowed to put 2 specimen in one vessel for Huey testing...

Thanks very much for your assessment!

Yes, it is. Very bright and with yellow color.

Hello and thanks for the replies, the reason for the high emissivity is the need for better radiative cooling. The eps=0.85 value comes from our thermal analysis guys. The 0.85 is the minimum acceptable value. There are many possibilities from the gas turbine industry involving a base layer...

Dear colleagues, Thank you for your replies. A coupon rack test is unfortunately not applicable here, because the real environment is a very small combustor using a hydrazine and NTO as fuel. So the real corrosion attack will be a combined intergranular attack (during non operating case, when...

Hi everybody, I am currently searching for a method to increase the total emissivity of a metallic surface to 0.85 or higher at temperatures up to 3000F (1650°C). There are many manufacturers of plasma sprayed coatings on the market stating that their products (like iron tianate, aluminium...

Dear colleagues! I am currently engaged in a project evaluating several Ni/Co/Fe-base cast and wrought super alloys with respect to their sensitivity towards wet intergranular corrosion. Within our product, temperatures up tp 1000-1500 F may occur, followed by colder phases where corrosive...

Hello! Perhaps my downstream pressure tap is too far awy from the orifice bore! So in the simpified discharge coefficient formula cd=dm/dt / A0*sqrt(2*rho*dp), the dp is the pressure drop without pressure recovery? So if my pressure tap is there where the flow is again fully expanded, my...

Thanks FredRoss! Ok, from Bernoulli and mass conservation formula I get: dm/dt is proportional to sqrt(rho *dp) from that follows: (dm/dt)**2 / rho is proportional to dp I want to have dp_water =! dp_other_fluid So I get from the formula above: const * (dm/dt)**2_water/rho_water = const...

Thank you very much for the helpful posts! But, I am not going to perform flow measurements, I have to measure the dp of the orifices. The orifices will later be uesed as trimming/calibration devices in a hydraulic application. Hacksaw, yes, it is still the same issue :) Today I again looked...

Hi Tom! I will do that. In one ore two weeks I will post the results; I have lots to do at the moment and this is not my main task. Greetings, Stephan

Dear colleagues! I have to measure the pressure drop of orifices. Now I am reflecting on my meausrement method. In the vicinity (up- and downstream) of an orifice, the flow is disturbed. After the orifice, the static pressure increases again while the streamlines are attaching again at the...