February 2020 Volume 2

FORGING RESEARCH

Laboratory Testing to Identify Permanent PVD Coatings to Minimize Lubricant Use During Forging: Final Report Trevor Kehe 1 , Spencer Randell 1* , Stephen Midson 1 ,

Andy Korenyi-Both 1,2 & Kester Clarke 1 1 Colorado School of Mines, Golden CO 2 Tribologix, Golden, CO *Currently at Weber Metals, Paramount, CA October 25, 2019

It is recommended that these coatings should be examined in more detail in future research. Future work should focus on the testing of PVD nanocomposite coatings that contain lubricious particles, and the development of coatings with even lower friction factors than the i-Kote and Super MoS 2 coatings examined in this study. Future work could include the following: • Optimization of these nanocomposite coatings • Identification of which lubricious particles provide the lowest friction factors • Identification of the optimumconcentration of lubricious particles • Determination of the optimum distribution of the lubricious particles within the thin-film coatings • Examination of the thermal stability of these types of coatings • Performance of higher cycle forging experiments at elevated temperatures Once the optimum coating has been identified based on the laboratory ring compression test, plant trials using coated forging dies should be performed to evaluate the long-term performance and stability of the coatings.

Executive Summary A laboratory test that provides a quantitative measurement of the impact of a range of substrate conditions on the level of friction between a forged aluminum workpiece and an H13 steel forging die has been identified and validated. The test, called the ring compression test, is easy to perform, and provides an excellent laboratory simulation of the metal deformation conditions present in commercial forging applications. A modified ring compression test apparatus has been designed and built that allows the examination of a range of substrate conditions on friction. Several forging conditions have been examined at both room and elevated temperatures (100°Cand200°C), including lubricated and un-lubricated, un-coated, nitrided, and a number of PVD coatings (i-Kote, Super MoS 2 , SiC, diamond-like carbon [DLC], TiCN and AlCrTiN). In the unlubricated condition, the lowest friction factors were obtained with two PVD coatings, i-Kote and Super MoS 2 . These are nanocomposite, thin-film coatings containing lubricious particles such as graphite and/or molybdenum disulfide (MoS 2 ). Based on the results of this study, the best coatings to provide low levels of friction during forging appear to be nanocomposite thin-film PVD coatings containing lubricious particles. These advanced coatings may thus allow for a reduction (or even possibly elimination) of the use of conventional lubricants during forging.

FIA MAGAZINE | FEBRUARY 2020 53