The effect of fretting at elevated temperatures on a clad material (65Au21Pd14Ag) and an electroplated soft gold over palladium-nickel material system

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 an alloy, 120 micro-in thick, consisting of 65% gold, 21% palladium, 14% silver over an 800 micro-in nickel sublayer. The other material system was 40 micro-in of electroplated soft gold over 80 micro-inches of palladium over 80 micro-in of nickel sublayer. Four different temperature levels were used during this research project. The temperature levels were 20, 50, 100, and 200/spl deg/C. Normal force was set at 200 g. Fret amplitude was 50 /spl mu/m. 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 m/spl Omega/. A four wire milliohmmeter 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 /spl Omega/. At room temperature, the clad material lasted 10 times as many fretting cycles than the soft 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 200/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 1600000 cycles. At 200/spl deg/C, the clad material lasted for 72000 cycles. The electroplated gold over palladium material system lasted for an average of 189000 cycles at 20/spl deg/C and 64600 cycles at 200/spl deg/C. In general, over the entire temperature range, the clad material was a much better contact material.