July_August_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 1 9 5 0 iTSSe TSS iTSSe TSS FEATURE COLD SPRAY METHOD HELPS RESTORE ANTIQUE VEHICLE Cold spray is uniquely suitable for depositing a wide range of materials over temperature-sensitive substrates. Julio Villafuerte CenterLine Windsor Ltd., Ontario, Canada BACKGROUND The Alfa Romeo 8C 2900B is a 180-hp detuned racing car, introduced in 1937 as a milder version of its 8C 2900 racing counterpart. Though less powerful than its predecessors, the 2900Bwas a sporty and exclusive auto for Alfa Romeo’s special clients. Due to its unique qualities, the car became an attrac- tive vintage automobile for avid international collectors. While the early history of the car discussed in this case study is un- clear, it is believed to have been kept inGermany throughWWII and the early 1950s. It may have been purchased by a British buyer after the war, and then in 1956, the 8C 2900Bwas sold to an American collector and brought to the U.S. [1] The car was first restored in the 1990s. It then traveled between the U.S. and Europe over the next few years before finally joining the collection of David and Ginny Sydorick. After winning the 2001 prize for Most Elegant Closed Car at the Peb- ble Beach Concours d’Elegance, the Alfa Romeo earned Best of Show at the 2003 European Concours d’Elegance. In 2010, it was shown at the 2010 Goodwood Festival of Speed and in 2018, the car won Best of Show at the Pebble Beach event [1] . RESTORATION ISSUES Corrosion along with standard wear and tear took a toll on the appearance and functionality of the cast aluminum oil pan of the vintage vehicle. Visible cracks on the inside of the pan resulted in oil leaks, which were detrimental to the aes- thetics of the pan’s exterior (Fig. 1). The cast aluminum alloy used to fabricate the oil pan was originally heat treated and therefore sensitive to thermal repair processes such as welding and conventional thermal spray, which create heat-affected zones and distortion. Be- cause replacing the vintage component was simply not an option, attempts were made to repair a number of defects as well as restore the part to its original dimensions using known methods. Unfortunately, these thermal techniques were not successful and only worsened the oil pan’s appearance. There- fore, another tactic was needed, not only to solve the oil leak and restore the aesthetics but also to fortify the mechanical integrity of the base material. SOLUTION Cold spray was investigated as a repair method that could resolve the issues mentioned above. The technique in- volves solid-state metal consolidation using a high-velocity gas jet to propel metal and other powder particles against a substrate where particles plastically deform and consolidate upon impact. The term cold spray refers to the relatively low tempera- ture involved in the process, which is typically much lower than the melt- ing point of the spray material and substrate. With Centerline’s SST cold spray equipment (Fig. 2), air, nitrogen, or helium can be used as a propellant gas and temperatures are low enough to avoid damaging the substrate ma- terial. After low-temperature dimen- sional restorationof the area, the new- 1937 Alfa Romeo 8C 2900B Touring Berlinetta. Fig. 1 — Visible cracks and unacceptable aesthetics in and around the oil pan. 10