The influence of hardening medium
in the vacuum carburizing process
on the distortion of machine elements
used in the automotive industry
Authors: Pawęta S. , Pietrasik R. 
Published: October 2019

Purpose: As part of this study, the influence of the hardening medium on distortions of
FineCarb® carburized rollers used in the automotive industry as elements of fuel pumps has
been examined. The analysis was carried out for the process of quenching in gas at different
pressure of cooling gas and quenching in oil at variable delay time of oil mixers.
Design/methodology/approach: The research was carried out on real elements used
in the automotive industry as elements of fuel pumps. FineCarb® vacuum carburizing
technology was used in order to obtain optimal parameters of the surface layers. During
quenching a variable related to the parameters of the quenching medium was introduced.
For quenching in gas it was the pressure at which nitrogen was introduced into the cooling
chamber, while for quenching in oil it was the time of mixers delay. The sample batch was
laid out in accordance with the PPAP (Production Part Approval Process) requirements for
the automotive industry. Microhardness and radial runout measurements were carried out
on the samples and subjected to statistical analysis.
Findings: The analysis of each hardening processes has showed that depending on
the cooling medium used, different distortion values are obtained. The distortion value
is significantly influenced by the parameters of the hardening process – gas pressure/oil
mixers delay. With the proposed quenching parameters, there is no relationship between
the location of the sample in the furnace chamber and the distortion value. The smallest
hardening distortions were obtained as a result of the hardening process in gas at a gas
pressure of 3 bar. Hardening in gas was characterized by the smallest scatter values of
obtained results of radial runout.
Research limitations/implications: Basing on the studies and analyses carried out in
this work, it can be concluded that the introduction of gas quenching technology instead of
oil quenching technology is justified qualitatively and economically alike. Hardening in gas
was also characterized by the smallest scatter values of obtained results of radial runout.
This is an extremely important technological and economic aspect, due to the cost of
grinding processing.
Practical implications: The automotive and aviation industries are putting ever
greater demands on the quality of manufactured components while reducing costs.
Volume 94 • Issues 1-2 • May-June 2019
It requires optimization of technological processes from co-operators. In the case of
hardening plants, the most important aspect is obtaining repeatable, precisely planned
parameters of the carburized layer, as well as minimizing the negative phenomena that
cause dimensional changes after hardening of elements. The tests allowed to determine the
most effective hardening conditions in terms of obtained distortions and costs of eliminating
distortions. However, the selection of the optimal parameters depends on whether the core
hardness requirements are also determined.
Originality/value: The conducted tests allowed to determine the most effective hardening
conditions in terms of obtained distortions, costs of levelling distortions and a complete
technological process for the automotive industry.