S45C steel is a medium carbon steel that is popular due to its affordable price, as
well as its hard, wear-resistant, and ductile properties. This study aims to examine
the effect of hardening, quenching, and tempering processes with variations in
tempering temperature on the hardness, impact toughness, and microstructure of
S45C steel. Heat treatment was carried out by hardening at 930°C for 30 minutes,
followed by quenching with oil media, and tempering at 230°C, 330°C, and 500°C.
Tests included Rockwell hardness, Charpy impact, and microstructure analysis. The
results show that the tempering process reduces the hardness of S45C steel from
18.6 HRC (raw material) to 8.3 HRC. The hardness decreased as the tempering
temperature increased. In contrast, the impact toughness increased from 0.327
J/mm² in the raw material to 2.158 J/mm² after tempering. The microstructure of
the raw material consists of ferrite and perlite, while after heat treatment it changes
to ferrite, tempered martensite, and a little perlite