A comparison of a clad material (65Au21Pd14Ag)
and an electroplated gold over Palladium material
system under fretting conditions at elevated temperatures.
Neil Aukland: New Mexico State University
Harry Hardee: New Mexico State University
Anna Wehr-Aukland: New Mexico State University
Phillip Lees: Technical Materials Inc.
Abstract
Fretting experiments were conducted on two different material systems at elevated temperatures. One of the material systems was a clad material. The clad material was 120 micro-inches thick of an alloy consisting of 65% gold, 21% Palladium, 14% silver over an 800 micro-inch nickel sublayer. The other material system was 40 micro-inches of electroplated soft gold over 80 micro-inches of Palladium over 80 micro-inches of nickel sublayer. Four different temperature levels were used during this research project. The different temperature levels were 20, 50, 100 and 200o C. Normal force was set at 200 grams. Fret amplitude was 50 microns. The fretting frequency was 8 Hertz. Some limited fretting experiments were conducted using a new contact lubricant (CLT: X-10). Contact resistance data were collected on the number of cycles to reach specific contact resistance levels. These levels were 10, 50, 100 and 250 milliohms. A four wire milliohmmeter, specifically designed to collect contact resistance values, was used to collect the data. A material study was conducted as part of this project.
The two different material systems were compared using a simple t-test, based on the number of fretting cycles to exceed 0.25 ohm. At room temperature, the clad material lasted 10 times longer than the gold over Palladium material system. At 50 and 100o C the clad material was still better than the gold over Palladium material system, but the overall improvement in fretting performance had decreased. At 50o C, the clad material lasted 3.2 times longer than the electroplated gold over Palladium. The improvement in fretting performance by the clad material at 100o C was slightly better and the clad material lasted 5.8 times longer than the gold over Palladium material. At 200o C, the clad material was only slightly better than the gold over Palladium material system. If the number of cycles to failure at 20o C is compared to the number of cycles to failure at 200o C for both material systems, the increase in temperature caused a decrease in fretting performance. The average cycles to failure at 20o C for the clad material was 1,600,000 cycles. At 200o C, the clad material lasted for 72,000 cycles. The electroplated gold over Palladium material system lasted for an average of 189,000 cycles at 20o C and 64,600 cycles at 200o C. In general, over the entire temperature range, the clad material was a much better contact material.
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