Abstract
Laser surface treatment on two different types of nickel–chromium white cast iron (Ni-hard) alloys (Ni-hard 1 and Ni-hard 4) was investigated. Nd:YAG laser of 2.2-kw with continuous wave was used. Ni-hard alloys are promising engineering materials, which are extensively used in applications where good resistance to abrasion wear is essential. The conventional hardening of such alloys leads to high wear resistance nevertheless, the core of the alloy suffers from low toughness. Therefore, it would be beneficial to harden the surface via laser surface technology which keeps the core tough enough to resist high impact shocks. A laser power of different levels (600, 800 and 1000 Watts) corresponding to three different laser scanning speeds (3, 4 and 5 m·min−1) was adopted hoping to reach optimum conditions for wear resistance and impact toughness. The optimum condition for both properties was recorded at heat input of 16.78 J·mm−2. The present findings reflect that the microhardness values and wear resistance clearly increased after laser hardening by almost three times due to laser surface hardening, whereas, the impact toughness was increased from five joules obtained from conventionally heat-treated samples to 6.4 J as gained from laser-treated samples.
Highlights
Ni-hard is the common name for a family of white cast irons alloyed with nickel and chromium which are known of their high hardness and outstanding resistance to abrasion wear
After Laser Heat Treatment (LHT) Sample 1 (S1) and Sample 2 (S2) samples have both impact energy higher than that which was obtained from conventional heat treatment (CHT) samples despite the close values of the surface hardness levels that was achieved after both treatments
The present data confirm that the impact energy is practically independent on the laser heat input values whereas, S2 impact level is higher than S1
Summary
Ni-hard is the common name for a family of white cast irons alloyed with nickel and chromium which are known of their high hardness and outstanding resistance to abrasion wear. These alloys are extensively used in mining and mineral processing industries, such as hammers, crushers, ball mills and pulverizing rolls [1,2]. Ni-hard 1 alloys contain about 44% M3 C type carbide embedded in an iron matrix [4] Their solidification begins with formation of proeutectic austenite followed by eutectic reaction
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