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

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 degrees C. Normal force was set at 200 g. Fret amplitude was 50 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 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 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 degrees 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 degrees 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 degrees C was slightly better and the clad material lasted 5.8 times longer than the gold over palladium material. At 200 degrees C, the clad material was only slightly better than the gold over palladium material system. If the number of cycles to failure at 20 degrees C is compared to the number of cycles to failure at 200 degrees C for both material systems, the increase in temperature caused a decrease in fretting performance. The average cycles to failure at 20 degrees C for the clad material was 1600000 cycles. At 200 degrees C, the clad material lasted for 72000 cycles. The electroplated gold over palladium material system lasted for an average of 189000 cycles at 20 OC and 64600 cycles at 200 degrees C. In general, over the entire temperature range, the clad material was a much better contact material.