Laser Surface Hardening of Ni-hard White Cast Iron

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.