Abstract
DIN 15CrNi6 is the most representative grade of the case-hardened steels. The present work analyses the influence of carburizing time on hardness of the specific steel. Specimens with similar chemical composition were heated at 900°C in liquid carbonaceous media for one, two, three and four hours, correspondingly. Then samples were oil quenched and tempered at 180°C for two hours. Microhardness was measured across the carburized zone and case profiles were acquired. The effective case depth was determined as function of carburizing holding time. Core macro hardness was carried out and the impact of holding time on the substrate hardness was discussed. The optimum case depth was defined and the carburizing parameters determined. The hardness control is critical in case hardening practice and results provide practical information to heat treaters, useful both to control the treatment parameters and to minimize the risk of failure.
Highlights
Carburizing is the most common surface engineering procedure
The analyses of hardness behaviour as function of the carburizing time resulted in the construction of a case profile and allowed the measurement of the effective case depth
Investigation showed that carburizing until two-hour exposure at 900oC, in liquid carbonaceous media, resulted in poor and inhomogeneous case
Summary
Carburizing is the most common surface engineering procedure. The process involves the diffusion of carbon into the surface of low carbon steels (non-hardenable steels), by exposing them in a carbonaceous environment [1]. The case depends on the carburizing temperature, the holding time, and the available carbon potential at the surface [5, 6]. The effective case depth represents the distance inner from the surface to a definite hardness. They are several techniques to estimate the case depth and the results determined are different [19]. The effective case depth (ECD) is defined as the vertical distance from the surface to the layer hardened to 550HV [20]. Optimal service life Bending and torsion fatigue Bending and torsion fatigue Abrasive wear Torsion fatigue Through hardening CHD=3-4 times the depth of maximum stress
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