Analisis Pengaruh Preheat Pada Proses Hardfacing Overlay Material Hardox 450 Terhadap Nilai Kekerasan, dan Struktur Mikro

Abstract

Hardfacing overlay is a hardening of the metal surface by depositing the metal surface
with filler metal which has a high hardness value. In the results of hardfacing overlay using Hardox
450 material with high hardness, there are often large cracks caused by the presence of two equally
hard phases. The way that can be done in order to minimize the occurrence of cracks is to use
preheat. The higher the preheat temperature and the longer the holding time is believed to reduce the
risk of crack occurrence. Based on its carbon equivalent, Hardox 450 material needs to be preheated
at 95?. This study compares the hardness value and microstructure that occur after the hardfacing
overlay process between specimens with 95? preheat and without preheat. The resulting hardness
value shows the highest hardness value obtained in the specimen without preheat, namely at the base
metal of 343.48 kgf/mm 2 and in the hardfacing layer area of 476.92 kgf/mm 2 . The microstructure
resulting from the hardfacing process overlaying Hardox 450 material is quite complex. In the base
metal the resulting microstructure is not much different, dominated by the tempered martensite
structure. In the buffer layer area the resulting microstructure is austenite and verimicular ferrite
structure. In the hardfacing layer area the resulting microstructure is a dendritic phase form between
austenite and lathy ferrite.