CrC-NiCr cracking network

[louishong]

Hi, We are facing cracking issues on the HVOF coating, below are some basic info:

Product: 48 inch valve stem, used on O&G industry, high temperature 700 C max, high erosion environment exposure to propane, hydrogen)

Base material: 1.4988/X8CrNiMoVNb 16-13, austenitic steel

Coating: Oerlinkon-Metco 81VF-NS, applied by HVOF, Cr3C2-NiCr. Coated stem will slide on the Valve packing(graphite) and guide bushing(cast iron)

Finished stem: after coating&grinding: PT-dye penetration shows no defects at room temperature

After hot test: Stem was assembled into Valve, and Valve assembly was hot function tested at 650 C, heating/cooling rate is below 25 C/hour. After hot test, PT shows cracking network

 

We discussed with our HVOF supplier, coating thickness shall be 0.2mm after grinding according to the drawing, but our supplier said actual thickness is 0.3 to 0.5mm. the stem distortion is too much after spraying, so they have to reduce the O.D. of the base material, and spray more,

 

We are deeply concerned with the quality and life of coating, can you pls help to analyze the root cause of cracking? Is it normal for the CrC-NiCr to crack after heating/cooling cycle? Is it easy to flake off as the stem will slide 8000 times each year?

[louishong]

Hi, We are facing cracking issues on the HVOF coating, below are some basic info:

Product: 48 inch valve stem, used on O&G industry, high temperature 700 C max, high erosion environment exposure to propane, hydrogen)

Base material: 1.4988/X8CrNiMoVNb 16-13, austenitic steel

Coating: Oerlinkon-Metco 81VF-NS, applied by HVOF, Cr3C2-NiCr. Coated stem will slide on the Valve packing(graphite) and guide bushing(cast iron)

Finished stem: after coating&grinding: PT-dye penetration shows no defects at room temperature

After hot test: Stem was assembled into Valve, and Valve assembly was hot function tested at 650 C, heating/cooling rate is below 25 C/hour. After hot test, PT shows cracking network

 

We discussed with our HVOF supplier, coating thickness shall be 0.2mm after grinding according to the drawing, but our supplier said actual thickness is 0.3 to 0.5mm. the stem distortion is too much after spraying, so they have to reduce the O.D. of the base material, and spray more,

 

We are deeply concerned with the quality and life of coating, can you pls help to analyze the root cause of cracking? Is it normal for the CrC-NiCr to crack after heating/cooling cycle? Is it easy to flake off as the stem will slide 8000 times each year?

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[/img]

[louishong]

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[/img]

[louishong]

see attached picture

[Vadim Verlotski]

Your problem has a very simple explanation: the coefficient of thermal expansion of the CrC-NiCr coating (about 10x10-6K-1) is significantly lower than that of austenitic stainless steel (about 17x10-6K-1). In combination with the high modulus of elasticity of the coating, this leads to high tensile stresses in the coating when heated, which induce a network of cracks.
In order to solve this problem, there are two possibilities: either use another coating with a higher thermal expansion coefficient and a lower modulus of elasticity, or use a thick sublayer of an easily deformable material, such as nickel-aluminum.
Taking into account the fact that you do not spray the valve yourself, but depend on the supplier, the easiest solution for you will be the second option: spray 0.2-0.3 mm of Ni-Al coating on the stem, and no more than 0.2 mm on top  CrC-NiCr.

[louishong]

Hi Vadim, thanks for your explanation and suggestion, we will consider to change the coating system. Do you have further comments regarding the cracked Stems, how far betwwen cracking and flake off?couple of weeks or months? we have some valves which are not hot tested delivered to customer, becausure Hot test are not 100% according to our contract. and we are considering to recall these Valve, if there is high risk of stem coating flake off which will lead malfunction of the Valves.

[Vadim Verlotski]

Dear Louis,
If you did not use an undercoat, but applied the CrC-NiCr coating directly to the steel, then the chance of peeling this coating when operating above 600°C is 100%. The coating will definitely peel off, but it is not known how long it will take. The fact is that the CrC-NiCr coating allows air to pass through, which oxidizes the surface of the steel underneath. After some time at high temperature, the oxide layer on the steel reaches a critical thickness and the coating peels off. There are two commercial underlayer materials that improve the situation, nickel-aluminum and MCrAlY (M = Co, Ni oder Fe), which is used for gas turbines. Of these undercoats, nickel-aluminum is cheaper, easier to apply, and performs well up to 700 degrees. The advantage of MCrAlY is a higher application temperature (up to 1000 degrees).