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This study has used a simple method to predict wear of die coatings used in the strip ironing of steel sheet based on Archard’s wear model by using finite element (FE) simulation. This method required the information regarding the quantity of worn material and thickness of die coatings. The die stresses obtained from the FE simulation were used to calculate the wear rate and wear depth per cycle. The die and sheet materials considered were D2 tool steel and S690QL, respectively. Two types of die coatings (CrN and TiN) and their known properties were studied. The studied sliding velocities were 0.1, 1.0 and 5.0 mm s−1. The contact pressures under investigation were 15, 150 and 1500 kPa. The results showed that TiN provided higher wear resistance due to its lower quantity of worn material (1.962 × 10−16 m3). The total wear depth per cycle increased with reducing quantity of worn material (increasing hardness value). Increase in sliding velocity led to increase in wear depth per cycle. The contact pressure (15–1500 kPa) did not significantly affect wear depth per cycle. To illustrate the acquired wear depth per cycle of all the coatings under different conditions, a predictive wear map was developed. In addition, the number of operating cycles based on the die coating thickness could be calculated. Based on the findings, the wear map could be used to help select appropriate die coatings and adjust process parameters in order to extend die service life. [ABSTRACT FROM AUTHOR]

Abstract: Sheet metal forming processes usually involve a sliding contact between the blank and tool surfaces, thus requiring the use of lubricants to prevent severe tribological conditions at the tool–workpiece interface. However, improper lubrication policies may have a negative impact on the environment, due to the use of unhealthy degreasing agents to wash the formed parts. In recent years, the introduction of the diamond like carbon (DLC) coatings has represented an attractive solution for the development of dry or nearly-dry forming processes. To be effective, these coatings must strongly bond to the dies substrate in order to grant resistance to the abrasive and adhesive wear. Although many approaches for evaluating the tribological performances of such coatings can be found in the existing literature, they often suffer from limitations in reproducing the interface conditions typical of the industrial processes. The objective of the present research work is to investigate the tribological behaviour of DLC coatings applied to sheet-forming tools under process conditions compared to the ones experienced by the traditional coatings used in industry. Experimental values of the friction coefficient have been determined by means of strip drawing tests and the coatings wear and adhesion to the substrate have been investigated by means of pin-on-disk and scratch tests. [Copyright &y& Elsevier]