Abstract
The aim of this study was to provide an experimental investigation on the novel method for recycling chips of duplex stainless steel, with the addition of vanadium carbide, in order to produce metal/carbide composites from a high-energy mechanical milling process. Powders of duplex stainless steel with the addition of vanadium carbide were prepared by high-energy mechanical ball milling utilizing a planetary ball mill. For this proposal, experiments following a full factorial design with two replicates were planned, performed, and then analyzed. The four factors investigated in this study were rotation speed, milling time, powder to ball weight ratio and carbide percentage. For each factor, the experiments were conducted into two levels so that the internal behavior among them could be statistically estimated: 250 to 350 rpm for rotation speed, 10 to 50 h for milling time, 10:1 to 22:1 for powder to ball weight ratio, and 0 to 3% carbide percentage. In order to measure and characterize particle size, we utilized the analysis of particle size and a scanning electron microscopy. The results showed with the addition of carbide in the milling process cause an average of reduction in particle size when compared with the material without carbide added. All the four factors investigated in this study presented significant influence on the milling process of duplex stainless steel chips and the reduction of particle size. The statistical analysis showed that the addition of carbide in the process is the most influential factor, followed by the milling time, rotation speed and powder to ball weight ratio. Significant interaction effects among these factors were also identified.
Highlights
Duplex stainless steels (DSS) are two-phase austenite (γ-CFC) and ferrite alloys which are capable of combining the good properties of ferrite and austenitic stainless steels [1,2,3,4]
The mathematical mathematical model model for for factorial factorial planning planning 2244 is given by Equation (1), where R is the average size of the particle and Rs, Mt, Pr, Cp mean rotation speed, milling time, powder to ball weight ratio and carbide percentage, respectively
The high-energy milling process is an alternative route to the the reuseof of stainlesssteel steel chipswith with andwithout withoutaddition additionofofVC
Summary
Duplex stainless steels (DSS) are two-phase austenite (γ-CFC) and ferrite alloys which are capable of combining the good properties of ferrite and austenitic stainless steels [1,2,3,4]. Duplex stainless steels are mainly used in the following industries: pulp and paper, disinfection of plants, gas flue cleaning, heat exchangers, and the nuclear and chemical industries [5,6,7]. Stainless steel production is one of the most important and fastest growing metallurgical industries in the world. The world production of stainless steel reached approximately 45.8 million tons in 2016, an increase from the. 41.5 million tons produced in 2015 [8]. The use of the high energy milling process is an alternative for the reuse of this material. Reutilization of recycled materials has as a main objective the reduction of environmental impact and rationalization of energy chains [9]. Stainless steel components produced by powder metallurgy comprise an important and Metals 2019, 9, 842; doi:10.3390/met9080842 www.mdpi.com/journal/metals
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