PHYSICS OF STRENGTH AND PLASTICITY PACS numbers: 61.66.Dk, 62.20.Qp, 81.40.Cd, 81.40.Ef, 81.65.-b, 81.70.Bt Hardness Uniformity in AISI 4140 Using Spray Quenching Method Mochamad Achyarsyah and Poppy Puspitasari *,** Bandung Polytechnic of Manufacturing, Foundry Department, 21 Kanayakan Str., ID-40135 Bandung, West Java, Indonesia * State University of Malang, Mechanical Engineering Department, 5 Semarang Str., ID-65145 Malang, East Java, Indonesia ** State University of Malang, Centre of Advanced Materials for Renewable Energy, 5 Semarang Str., ID-65145 Malang, East Java, Indonesia Bucket teeth are a part of the coal process circuit in bucket excavator machine. It is used to dredge the overburden or a piece of the land that covers coal piles. Bandung Polytechnic of Manufacturing produces the product with AISI 4140 steel. The problem with batch production is that it has a wide variety of hard- ness as the result of using a quenching by blower. Therefore, there needs an alternative to a thinner hardness of bucket teeth. This research explores the possibility of using spray quenching method. The method uses the spray to quench the samples on the rotated concrete steel shelf evenly. The Shore sclero- scope hardness test performs three times on the products at two points: the tip and 80 mm from the tip. The results are averaged later on. They show that spray quenching produced a thinner hardness variety compared to the blower product. Product using blower has the hardness of 25.16 HRB at point 1 and 15.66 HRB at point 2. Product with the first spray quenching has the hardness of 15.1 HRB at point 1 and 11.56 HRB at point 2, and after the second spray quenching became 7.3 HRB at point 1 and 8.4 HRB at point 2. Thus, spray quenching provides a more uniform hardness along the teeth and can be a sub- stitute for the traditional quenching method. Corresponding author: Mochamad Achyarsyah E-mail: achyarsyah@polman-bandung.ac.id Citation: Mochamad Achyarsyah and Poppy Puspitasari, Hardness Uniformity in AISI 4140 Using Spray Quenching Method, Metallofiz. Noveishie Tekhnol., 42, No. 3: 401– 414 (2020), DOI: 10.15407/mfint.42.03.0401. Metallophysics and Advanced Technologies Ìåòàëîôіç. íîâіòíі òåõíîë. Metallofiz. Noveishie Tekhnol. 2020, vol. 42, No. 3, pp. 401–414 https://doi.org/10.15407/mfint.42.03.0401 Reprints available directly from the publisher  2020 G. V. Kurdyumov Institute for Metal Physics, National Academy of Sciences of Ukraine Published by license under the G. V. Kurdyumov Institute for Metal Physics– N.A.S. of Ukraine Publishers imprint. Printed in Ukraine. 401