Deformation of Exposed Tool Parts for Crushing of Undesirable Advance Growth

Abstract

Tools for crushing of undesirable advance growth and mulching wood are subjected to heavy wear in operation with the need for their frequent replacement shortly after deployment. It is important to address the problem of their wear due to price of tools, as well as the time necessary for their replacement. Tool life is shortened because of deformation taking place due to the loss of wolfram-carbide (WC) tips, what is an undesirable phenomenon. Solutions for increasing the tool lifetimes were designed on the basis of analysis of wear mechanisms that cause this deformation. Furthermore, effect of deformed layer was evaluated by measuring hardness and microhardness. It was found that there was a strain hardening the surface due to cyclic loading. Size and extent of deformation of the entire tool with the loss of material on the functional part were documented using an optical scanning sensor system. Effect of the deformation on the material structure change, as well as topography and extent of surface area affected by abrasive wear under impact loads, were assessed by means of light and electron scanning microscopy. On the basis of these analyses, an option for increasing the lifetime of exposed areas on the tool by application of hardfacing to increase the tool wear resistance was proposed. Prerequisite for extending their work lifetime in the field is creation of a sufficient coarse layer or multiple layers of wear resistant material at specific tool areas.

Analysis of Hard Facing Material Designed for Application on the Forestry Tools

“…The increased hardness does not automatically mean better wear resistance or longer durability. The metal matrix must resist the scaling effect of the particles and also must prevent the carbides from breaking [9,13].…”

“…According to the results in reported [13], the significant plastic deformation formed below the surface from the cyclically repetitive abrasive load of the tool surface (high speed of the adapter rotor) causes the tool surface to harden. This is manifested by the separation of material parts ( Fig.…”

“…They are made by means of thermoforming technology, so they are forgings. According to the research reported in [13,6], the tools made of 15MnCr5 steel do not meet the conditions under which they work, because of their mechanical properties and a ferritic-pearlitic structure in not heat-treated state after losing the WC tips mounted on the tool body. They are object of strong abrasive wear in the heterogeneous environment, which is associated with shock loading.…”

“…The coefficient values of weight loss W h , relative abrasion resistance ψ h and coefficient of hardness K T are given in Table 4. For comparison, the table also contains the etalon values obtained by the experiment published in [13].…”

“…They operate in a heterogeneous environment where they are subject to abrasive wear. This results in their relatively early decommissioning [13]. At the same time, their price is a significant item for forestry companies.…”