Wyniki 1-1 spośród 1 dla zapytania: authorDesc:"Jacek Czop"

The effect of grit-blasting on the formation of a carburized layer in the vacuum carburizing DOI:10.15199/28.2019.5.1

  1. INTRODUCTION Low pressure carburizing (LPC) is a case-hardening process which over the past decade has become used in the aviation industry high volume automotive transmission gears [1, 2]. The reason for that was its features in comparison to conventional atmosphere (gas) carburizing such as: excellent uniformity and repeatability, lack of intergranular oxidation, environmentally-friendly and cost-effective. In terms of mechanical properties vacuum carburizing results in a high hardness and wear resistant surface with load-bearing core [3, 4]. LPC as a non-equilibrium process need to be designed by computer modelling. Currently, the mathematical models which describe the mechanisms of vacuum carburizing and associated with the use of numerical methods allow to predict appropriate carbon concentration profile in the diffusion layer [5÷8]. As a result, repeatable hardened layers is created in LPC with followed heat treatment. This reduces the empirical determinations of the process factors which consume much time and costs. The LPC process is running in a condition of low vacuum (1÷10 hPa) created by a small amount of carburizing gas (acetylene, ethylene or their mixture with hydrogen). The carbon atoms are created as a result of catalytic decomposition of aliphatic hydrocarbons at a temperature within the range of 900÷1050°C [9÷11]. Under this conditions the carbon potential of atmosphere is extremely high. Hence, LPC process consist of cyclically repeatable stages: saturation (“boost") and diffusion. In the boost stage, the surface of the metal is almost fully filled with carbon deposit during continuously supplied carburizing atmosphere [1, 7]. Kula et al. reported that decomposition products on the surface appears in two morphological phases: a thin film of an excess carbon and carbides [1, 12, 13]. The carbon diffuse into the metal up to solubility limit in the austenite and then carbides are formed. The excess ca[...]

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