Chromium Carbide Hardfacing for Slurry Transport Pipes

[Guest102023]

I am researching this class of hardfacing alloy for 24~36" carbon steel pipes (and elbows) for transport of sand-bearing slurry in slightly acidic water. The primary wear mode is corrosive-abrasive wear. Clad thickness is 1/4~5/16 inch. The object is to improve service life.

Chromium carbide (CC) hardfacing (~30% Cr, 4-6% C) is the industry standard, but for the proposed environment suffers from lack of corrosion resistance. It is also vulnerable to weld cracking down to the CS substrate, leading to rapid corrosion and other more drastic wear modes (large chunks breaking off). What I've found so far is that ~30% blocky primary carbide phase (Cr7C3) is optimum for abrasion resistance; I know less about the matrix structure. The composition relative to the eutectic point appears to be a major factor influencing properties. Abrasion resistance and hardness properties (>50 HRC) are fairly easy to achieve; corrosion resistance and fracture toughness are more elusive.

I am seeking experiences from metallurgists/welding engineers, fabricators and end users. Welding processes/techniques, electrode vendors (I prefer subarc), composition, effects of additional alloying elements (B, Ti, Mo, Ni, ...), any and all pitfalls. Ideally the matrix would be austenitic stainless for toughness and corrosion resistance, but is it possible? Micrographs with descriptions are most welcome.

 

[Guest102023]

Correction - this problem is probably better described as erosive wear.

 

[berkshire]

Brimstoner,
Not wishing to set you off on a tangent, have you investigated cast Basalt liners for that application?

http://www.abresist.com/ABRESIST_Linings.htm

B.E.

 

[Guest102023]

Thanks berkshire, that looks interesting, but is outside of what my client is looking for.

 

[redpicker]

The Chromium Carbide hardfacting materials covers a wide range of materials. Many of compositons that have the highest abrasion resistance have a carbon content so high that you will form a continuous layer of Chromium carbide at the fusion line in the cladding, which will lead to spalling of the applicaiton under impact loads. The high carbon content also results in a very brittle structure, that as you have noticed, cracks easily; just the thermal contraction from welding temperatures will cause cracking.

There are other materials out there. Some are more crack resistant than others. In my experience, you will sacrifice some abrasion resistance to achieve a crack-free applicaiton, so you will have a trade-off.

There are other hardfacting materials that you may want to investigate. The Titanium Carbide materials will give nearly the same abrasion resistance with less cracking. There are also Boron-based (as opposed to Carbon-based) materials that may hold promise.

rp

 

[rmw]

Your client would be wise to back up and take a look at basalt lined pipe for this application.

rmw

 

[rmw]

Sorry, meant to stick this link in before posting:

http://www.cbpengineering.com/pdf/CBP-Basalt_Pipe.pdf

rmw

I have used beaucoup chrome carbide plate as fan and ductwork liners for gas sterams laden with abrasive materials - and it was just dandy. Those however, were dry processes where the myriad of surface cracks present offered no particular disadvantage. The substrate carried the stress load. People who were serious about slurry pipelines used Basalt. The planned to turn the pipe 120 degrees every 10 years in order to get a 30 year life out of the pipe. Others just replaced entire pipe runs more often.

 

[Guest102023]

How is the impact resistance of basalt? Because in addition to sand in the slurry there are small rocks. Resistance to impact loading is a distinct weakness of several classes of welded hardfacing.

 

[weldmetengr]

What about Iracore? It's used in Slurry Hydrotransport

http://www.iracore.com/lined-pipe-system.aspx

 

[rmw]

My main experience with basalt lined pipe was in coal bottom ash slurries and that flow stream is full of clinkers that are not only lava hard, but with lots of sharp edges too. Some of the pumps that pumped the stuff were designed to handle up to 14" solids. It was very tough stuff, not brittle at all.

rmw

 

[EdStainless]

What about HVOF? I have even seen coatings put down in two layers. Lots of options such as WC in a Cr/Ni matrix. Very tough and corrosion resistant.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[apecush]

Not sure how far application methods for ID surfaces have progressed since I got out of the industry, but PTA hardfacing with WC might be an alternative. Done correctly, it shouldn't crack, and NiCrBSi matrix does pretty well in corrosive environments. May be prohibitively expensive though.

 

[Guest102023]

apecush, redpicker

One of my project goals is overcoming the poor impact resistance and erosion-corrosion properties of CrC hardfacing. Do you know of formulations that give a tougher and more corrosion-resistant matrix? There are big trade-offs in this game, but I am prepared to give up some of the abrasion resistance and hardness that the CrC class has in abundance. Cost is not the foremost consideration at this point in time.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[redpicker]

brimstoner
You may want to check out Hardface Technologies from Postle Industries; they are rather knowledgeable and have a wide range of products.

rp

 

[arunmrao]

brimstoner,

I would go with rmw's recommendation of using ceramic tiles. These last long , are abrasion resistant and can withstand impact. The only consideration is cost.

In thermal power stations, where a lot of coal is transported ( in countries like India, more rocks and less coal) they are standing the test.A few years ago for a coke oven plant in a large steel plant , 3 materials were tried, manganese steels, high chrome iron and ceramic liners. Manganese liners wore out in 2 weeks, high chrome liners in about 12 weeks, but the ceramic liners lasted very long without breakage. However the cost of these ceramic liners was very high , my high chrome liners was selected as candidate material for the purpose.

Just last week, I had supplied for a bentonite grinding plant, plough blades hard faced with high chromium content and a hardness of 550BHN. They wore away in just 5 days. I am still battling for a solution.