Wear Test And Testing Of Nitrided Tools With A Narrow And Deep Gap In Aluminium Hot Extrusion

Laboratory testing of extrusion tool wear is practical and less expensive than direct observation of wear on real tools during industrial operation. Its efficiency is expressed mainly as the control of influential parameters of tribological system, the way of mechanical loading, and as reduction of time needed for the estimation of tool life. In order to approach with our testing conditions to the true physical characteristics of hot extrusion process and to intensify (i.e. shorten) the process of wear analysis, a test named "block on disc" was developed, enabling a high normal pressure between aluminium and tool, and a good temperature control of A1 disc. A specially shaped tool with 1 and 4 mm narrow gap was developed to analyse the efficiency of nitriding process into the depth of narrow gaps. Two tool steels were used for worlung tools. Each type of mechanically made tool was gas or ionic nitrided in various nitriding equipments. In order to evaluate the applicability and the efficiency of testing, comparisons of wear-test results were made with test tools, exposed to simulated extrusion by determining of wear scar, or roughness and rnicrohardness, respectively.