53312

Finish for AISI 1095 blue tempered steel - flat spring application [New York] 

October 13, 2009

We are going to be using 1095 sheet material to make a flat spring. As part of the manufacturing process, we will be putting a thru hole in the spring as well as shaping the outside. This spring is used on a medical instrument and it most likely will experience exposure to a bleach / water cleaning solution (in case of a blood spill). The spring is used in a latch operation and will undergo about 4-6 actuations a day when loading or unloading our treatment kit - so the cycles over life are not that huge (3,000 would be a high number).

During a design review, the question came up about corrosion protection on the spring and particularly the edges. The spring itself is about .125" wide x .75" long x .020" thick. The spring undergoes about .060" deflection during it's operation and is sliding over a surface that has an electroless Nickel finish.

The reason we have chosen 1095 is because of it's high yield stress (>200 ksi). We are operating around 150 ksi max stress.

What options do I have for putting a finish on this part? Is electroless Nickel and option? There was a concern that the plating may crack under the deflection stress. I want to make sure I don't affect the temper of the spring during the finish process.

Gary Hartman
Product design engineer - Rochester, NY USA

If exposed to bleach 1095 will rust very quickly. Electroless nickel, if thick enough (.001" min) will be reasonably rust resistant and can be expected to flex some.

Make certain that the parts are closely inspected after plating to verify that adhesion of the nickel is good.

Jeffrey Holmes, CEF - Spartanburg, SC, USA

Jeff,

Thanks for your reply. I was thinking about Elect Ni but was concerned about the flex. I will make sure we have a note on our print to inspect the finish.

Gary Hartman
- Rochester, NY US