Strengthening Properties and Wear Resistance of the Cu-xNi-yCo-Cr-Si Alloy by Varying Ni/Co and Zr Addition

This work examines the effect of nickel (Ni) and cobalt (Co) concentrations on wear resistance behavior of Cu-xNi-yCo-Cr-Si (x = 8−9 wt%, y = 1−2 wt%) and the zirconium (Zr) addition, in order to obtain an alloy with similar or better properties than the C17510 alloy. In this study, hardness and wear resistance mechanism behavior were associated with the microstructure evolution of these alloys with different aging strengthening conditions. Different heat treatments (HT) were applied to three alloys Cu-8Ni-2Co-1.6Cr-2Si wt% (L1), Cu-8.5Ni-1.5Co-1.6Cr-2Si wt% (L2) and Cu-9Ni-1Co-1.6Cr-2Si-0.18Fe-0.3Zr wt% (L3), the properties obtained were compared with C17510 alloy. Specimens were characterized by different metallographic techniques; the microstructural characterization was made with scanning electron microscopy (SEM) and revealed regions of dendritic morphologies. The solidification sequence is primary Cu dendrites and some phases in the interdendritic regions. The solution heat treatment decreased (ST) the Hardness Rockwell B (HRB) and wear rate resistance, and there was an increase with the first aging heat treatment (HT1) for each alloy. The most outstanding combination of properties was found for Cu-8.5Ni-1.5Co-1.6Cr-2Si wt% alloy (L2C3) with 100 ± 1 HRB and specific wear rate resistance of 1.2 × 10−4 mm3/Nm, after the first aging heat treatment.

Effect of Retrogression and Re-Aging Heat Treatment on Hardness, Tensile Strength and Microstructure of 7075 Aluminum Alloy

Retrogression and Re-Aging (RRA) Heat Treatment improves the tensile of aluminum alloys. In this research, to study the effect of Retrogression temperature and Retrogression time on the hardness, tensile strength and microstructure of 7075 aluminum alloy, have been applied. Retrogression treatments at different temperatures 180°C, 240°C and 370°C for 30 min and 90 min. When the retrogression temperature was 180°C for 30 min, the alloy has reached its highest hardness and tensile strength; they were respectively 165 HB and 586 MPa. RRA treatment of aluminum alloy 7075 led to precipitate a smoother, more homogeneous, and denser phase compared to the T6 treatment.

Influence of Aging Heat Treatment on Pitting Corrosion Resistance of Martensitic Stainless Steel

In this research is to study the influence of the aging heat treatment on the pitting corrosion resistance of martensitic stainless steel (MSS), where a number of specimens from martensitic stainless steel were subjected to solution treatment at 1100 oC for one hour followed by water quenching then aging in the temperatures range (500-750) oC for different holding times (1,5,10,15&20) hr. Accelerated chemical corrosion test and immersion chemical corrosion test were performed on samples after heat treatment. The results of the research showed that the pitting corrosion resistance is significantly affected by the aging temperature. Where found that the aging samples at a temperature of 500 °C have the highest rate of corrosion which may be due to an increase in the ratio of the Delta type ferrite (δ-ferrite) and very soft precipitates from other phases of heterogeneous form in the basic martensitic phase; which leads to increased corrosion rate, whereas aging samples in the temperature range (550–650) °C have the smaller rate of corrosion values, this is due to the high volumetric ratio of remaining austenite. The aging samples at temperatures above 650 °C show an average corrosion rate. It was also found that the type of pits resulting from both the chemical corrosion tests and their shape were not related to the ferrite type and the carbides present in the microstructure