Investigations into wear and galling mechanism of aluminium alloy-tool steel tribopair at different temperatures

Aluminium-based alloys present a number of interesting properties, such as lower density, corrosion resistance, thermal and electrical conductivity and good recyclability. For this reason, there is a strong trend in increasing the use of these alloys, particularly in the automotive industry [1, 2]. However, aluminium alloys show poor formability at room temperature, and the production of complex components requires a series of high temperature forming processes, such as warm and hot forging, extrusion and hot sheet metal forming [3]. Forming aluminium in these conditions subjects the tools to severe adhesive wear and galling, leading to increased energy needs, shorter tool life, lower part quality and increased cost.In this work, the wear mechanisms generated by aluminium alloys on forming tools have been studied by means of linear reciprocating sliding tests, performed in an Optimol SRV equipment. Balls of two different compositions (AA2017 and 99% pure aluminium) were slid against DIN 1.2344 (AISI H13) tool steel samples with various surface finishes at temperatures up to 450 ºC. The resulting wear tracks were studied by means of confocal microscopy and electron microscopy (SEM/BSE).The main results show that the observed wear mechanisms are extremely dependent on the system temperature, ranging from pure abrasive wear to formation of layers of compacted aluminium debris and gross aluminium transfer in the form of lumps. The choice of aluminium alloy can be very relevant on the wear behaviour of the system. On the other hand, tool surface finish has a limited effect on material transfer. [1] Miller W S, et al. Recent development of aluminium alloys for the automotive industry. Materials Science and Engineering A 280 (2000), pp 37-49 [2] Toros S, Ozturk F, Kacar I. Review of warm forming of aluminium-magnesium alloys. Journal of Materials Processing Technology 207 (2008), pp 1-12[3] Hanna M D. Tribological evaluation of aluminium and magnesium sheet forming at high temperatures. Wear 267 (2009), pp 1046-1050Godkänd; 2012; 20120618 (leopel)