Abstract. The effect of quenching on the mechanical properties of medium carbon steels using coconut (CW) water, pap water (PW) and spent engine oil (SPE) which have been largely considered as wastes was investigated. All specimens were normalized at a temperature of 840°C in order to remove residual stresses induced during machining operations. Various specimens were heated to ranges of 730-790°C and soaked for the range of 30-60 minutes respectively. Brinnel hardness tester was used to obtain the hardness values while Testometric M500-50AT model machine was used for the tensile test of the specimens. The highest hardness value (609.97 BHN) was obtained from the specimen heated to 790°C quenched in pap water as compared with 166.4 BHN for the normalized as-received sample. The yield (YS) and ultimate tensile (UTS) strengths of the quenched specimens were better than the normalized as-received sample. SPEquenched samples yielded the highest YS and UTS combined. The hardness value increased while YS and UTS decreased with soaking time for different temperatures. The highest hardness value for the specimens was obtained from coconut and pap water. Rather than been considered as wastes, coconut water, pap water and spent engine oil can improve the mechanical properties of medium carbon steel when used as quenching media.

The paper focuses on collection of information on recent multifaceted usage of biomass materials with critical examination on its sustainability. The use of biomass is becoming popular, with wide global acceptance as it is considered as green technology. The use of biomass products across industrial parallels, the material combination and production processes were elucidated in this paper. Biomass materials are seen as affordable alternative to conventional materials for domestic and industrial applications. The multifaceted use of biomass, which includes, energy generation, metallurgical applications, construction purposes, reinforcement in metal matrix composite, microelectromechanical system, biochemical and traditional medicine were discussed. This underscores the need to develop a sustainable plan to meet with its diverse usage to be beyond laboratory efforts. This paper examined whether the availability of biomass can sustain its multifaceted usage or not. It also examined the modalities to ensure sustainable use of biomass. Different policies were highlighted and discussed in line with continuous multifaceted use of biomass.

Quenching is one of the major processes of heat treatment of medium carbon steel that aims at improving its mechanical properties. However, the effectiveness of this process is dependent on several control factors that must be maximized to obtain optimum results in terms of hardness, yield strength, ultimate tensile strength among others. This study aims at optimizing the process of improving the mechanical properties of medium carbon steel by varying some key factors like the quenchant used (A), heat treatment temperature (B), and soaking time (C). The measured responses in this study were the hardness, yield strength (YS), and ultimate tensile strength (UTS). Optimization was conducted in two stages. The first stage dealt with the mono-optimization of process parameters using Taguchi's Signal-to-Noise (S/N) ratio. A total of nine (9) experiments were performed based on standard L9 orthogonal array because each of the three control factors has three (3) levels. The second stage was multi-objective optimization using Taguchi-based grey relational analysis (GRA). The optimal conditions for hardness, YS, and UTS were obtained at A 2 B 3 C 3 , A 3 B 2 C 3 , and A 3 B 3 C 3 , respectively. Using ANOVA as statistical analysis, it was observed that the soaking time was the main control factor for all three measured responses (31.95% contribution ratio for hardness, 62.46%, and 66.76% for YS and UTS, respectively), while the quenchant had the least contribution. Analysis of the Taguchi-based GRA revealed that the results obtained are in total conformance to that of the Taguchi method, with soaking time having the highest contribution ratio of 69.41%.

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