Abstract
The paper presents study results of laser alloying of CT90 tool steel with an applied pre-coat of boron, molybdenum or a mixture of these elements. Pre-coats were applied on steel substrates in the form of a paste. The aim of the study was to investigate the microstructure, chemical and phase composition, microhardness and corrosion resistance of these newly-formed coatings. The laser alloying process was carried out using a diode laser with a nominal power of 3 kW. In this study a laser beam power of 900 W and a scanning speed of 48 mm/s were used. As a result of the laser beam action, the presence of three areas was observed in cross-sections of specimens: a remelted zone, a heat affected zone and the substrate. The properties of coatings enriched with both molybdenum and boron were better than those of the steel substrate, but only the use of a Mo-B mixture resulted in a significant improvement in microhardness and corrosion resistance.
Highlights
IntroductionIn order to optimize the production process and obtain required properties of the surface layer, numerous studies on various methods and techniques of surface treatment have been conducted
The problem of surface modification is an important aspect of material engineering
As a result of a laser alloying process using selected chemical elements and a diode laser beam a newly-formed microstructure consisting of three zones was obtained on a steel substrate
Summary
In order to optimize the production process and obtain required properties of the surface layer, numerous studies on various methods and techniques of surface treatment have been conducted. Diffusion processes are most frequently used methods of surface modification in industry. Interesting properties of layers are obtained using thermo-chemical treatment involving diffusion saturation of the coatings with boron [1,2]. The boronizing process executed on a steel substrate is characterized by obtaining layers with high hardness (up to 1800 HV) and good wear resistance. A typical diffusion boronized layer is composed of two phases: FeB and Fe2 B. The FeB phase has higher brittleness [3], which may be manifested by spalling and flaking from the substrate, it is modified by various methods [4,5,6,7]
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