A comparison of a clad material (65Au21Pd14Ag) and an electroplated gold over palladium material system under fretting conditions at elevated temperatures

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 200/spl deg/ C. Normal force was set at 200 grams. Fret amplitude was 50 microns. The fretting frequency was 8 Hz. 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 100/spl deg/C the clad material was still better than the gold over palladium material system, but the overall improvement in fretting performance had decreased. At 50/spl deg/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 100/spl deg/C was slightly better and the clad material lasted 5.8 times longer than the gold over palladium material. At 200/spl deg/ C the clad material was only slightly better than the gold over palladium material system. If the number of cycles to failure at 20/spl deg/C is compared to the number of cycles to failure at 200/spl deg/C for both material systems, the increase in temperature caused a decrease in fretting performance. The average cycles to failure at 20/spl deg/C for the clad material was 1,600,000 cycles. At 200/spl deg/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 20/spl deg/C and 64,600 cycles at 200/spl deg/C. In general, over the entire temperature range, the clad material was a much better contact material.