Analysis of a high temperature reciprocating hammer type impact wear apparatus

Impact wear can occur when objects collide repeatedly causing damage to the surface of one or both objects. The underlying mechanisms that result in material loss, or displacement, from the contact are primarily surface fatigue and plastic deformation. Adhesion, abrasion and oxidative wear also can occur depending on the contact geometry, the operating conditions, and environment. Temperature is a key parameter and, depending on the application, can accelerate the mechanisms that are dominant at lower temperatures or cause other mechanisms to increasingly contribute, often synergistically. This is particularly the case in applications, for example in the energy, process and aerospace industries, where complex mechanisms that translate and rotate large loads operate at temperatures at or exceeding the thermal limits of the materials they are necessarily made from. There are a number of reciprocating hammer type impact apparatus described in literature that can be used for fundamental investigations, but none are capable of achieving the necessary temperatures in the contact zone of between 600°C and 1250°C, indeed many solely operate at room temperature. As a consequence, there is little information about the mechanistic role of temperature in impact wear. This work, therefore proposes a new high temperature impact wear test rig, initially capable of running reciprocating impact wear tests at temperatures up to 750 °C. The design process and features are described before presenting the results of impact wear tests conducted using specimens manufactured from an austenitic chromium-nickel stainless steel (AISI 304) and a nickel-based superalloy (Inconel 625). The tests ranged from room temperature to 750 °C, rising in increments of 250 °C. Stainless steel experienced a greater wear rate with increasing temperatures, whilst the superalloy experienced a reduced wear rate with increasing temperatures. Reflections on the use of the apparatus are also offered to inform others of suggested best practice.