Trouble with expansion of Ni-resist Type 1 1

[kevlar49]

I noticed that in thread330-104700 there is a stabilization heat treatment required for Type 5B Ni-resist after machining (EdSTainless comment). What happens if you do not perform that heat treatment?

The reason why I ask is that we are currently experiencing problems with Type 1 Ni-resist (which I suspect might be Type 5). We used to purchase cast Type 1 Ni-resist in a cast form. Our shop makes bushings out of it. After final machining, they apply a liquid nitrogen quench to cause slight shrinkage in the bushing. However lately, they have been getting materials that they are being told are Type 1 Ni-resist but are expanding instead of contracting upon liquid nitrogen quench. I am in the process of verifying the chemistry of the good bushing material that we have gotten in the past and the bad stuff that we are getting now.

Has anyone experienced this before?

 

[EdStainless]

I doubt that anyone sent you T-5 in place of T-1 with the price of Ni today.
Are you sure that it is even Ni-Resist? Check that first, then take a piece and give it a high temp homogenization treatment and see if it still behaves the same way.


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[arunmrao]

Irrespective of the alloy being type Ni resist type 1 or its variant, what baffles me is the expansion phenomenon on cryo treatment. Contrary to conventional wisdom,it indicates an anomalous expansion behaviour. surprising!!.



" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke

 

[kevlar49]

I just got the chemistry results back. Both fall into the composition range for ASTM A436 Type I, but one could be a ductile iron and the other a grey iron.

I also have a few more interesting twists. I am doing some metallgraphy to verify things. Here is a summary of what I have:

"Good" material (shrinks when chilled)
Could be ductile iron based on Mg
Fe bal
Mn 0.913
Si 1.882
P 0.021
Cu 6.250
C 2.66
Mg 0.010
Ni 16.160
Cr 2.498
S 0.006
Sn 0.012
Al 0.02
non-magnetic

Bad
Fe bal
Mn 1.160
Si 2.3
P 0.165
Cu 6.080
C 2.710
Ni 14.377
Cr 2.075
S 0.032
Magnetic

 

[metengr]

Try to get your hands on this paper from the Nickel Developmental Institute

11018 - PROPERTIES AND APPLICATIONS OF NI-RESIST AND DUCTILE NI-RESIST ALLOYS (1998)
By Roger Covert, et. al., 1998 Ni-Resist austenitic alloy irons offer an outstanding combination of properties to meet a variety of industrial demands in withstanding the effects of corrosion, heat and wear. Provides comparative data on the varous grades of Ni-Resist including physical and mechanical properties, welding and heat-treatment procedures, and other data to assist in their specification. Provides typical applications for the various commercial grades.

PDF: 931.85KB Order by Mail

http://www.stainlesswater.org/index.cfm/ci_id/11842.htm

 

[metengr]

According to the paper above, the only truly "nonmagnetic" alloys are NiMn 13 7 (low cost version of Ni-Resist alloy family) and Ni-Resist D2, which do not fall under your reported chemical results.

As a side note, the minor amount of Mg would lead to the formation of spheroidal graphite in the ductile Ni-Resists. Only a small quantity of Mg is present (no mention of amount but small to me is what you reported).

 

[kevlar49]

Just did the metallography:
good material--had Type A flakes, austentic dendrites, and some interdendritic carbides revealed with Marbles.

Bad material--had Type D flakes, martensitic dendrites, and no carbide material.

Someone mentioned that the "bad" material might be dura-bar. Need to verify this.

Looks like I had unstable austenite that transformed during quenching hence the magnetism and the increase in size (martensite occupies a larger volume).

Question is do I control by the starting material used or can I heat treat to solve the problem.

More to come...


any comments?

 

[arunmrao]

undercooled graphite is normally seen in the rim,hich is not unusual. But the instability of austenite transforming into martensite is yet again intriguing.

A stabilization heat treatment prior to use should take care of most of your concerns.

As per the NiDi publication on magnetic properties I quote" The magnetic permeability of NiResists is strongly influenced by the presence of carbides. Since their number and size can depend on heat tretment and other factors,measurements of magnetic properties are often variable."

" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke

 

[kevlar49]

All thanks for your advice,

Problems appears to be that we cross the Martensite start temperature at liquid nitrogen temperatures. We solved the problem by not cooling below -100 F. The material that we had problems with was in fact Durabar. Its chemistry apparently is raising the Ms up to the liquid nitrogen temperature.

Here was our fix: "[Cooling the durabar to -100 F,]... the ni-resist material (2.000" dia w/3/16" wall thickness) shrunk .003" when quenched to -100 deg F and came back to its original size when it reached ambient temp. No distortions we noted. The material seemed to be slightly more magnetic than it was before quenching, this should not be a problem. We used isopropyl alcohol w/dry ice and were able to regulate the temperature by adding enough dry ice to get the temperature right at -100 F. Our digital thermometer is good for -310 deg F. Also (just for fun) we took the same piece of material and quenched it in liquid nitrogen (-305 deg F). The material grew by 0.010" and distorted out of round by 0.008" - 0.010" and stayed oversize when it reached ambient. So for now we will not use liquid nitrogen for cold quenching ni-resist material without first making a test piece. Unless anyone has any objections, we will proceed with the fabrication of bushings for [our pump]..."

Hope this is useful to someone in the future.

 

[arunmrao]

Kevlar Excellent and thanks for sharing the note with us. A star goes out for you.

" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke