Evaluation of Surface Roughness of Some Biomedical Titanium Alloys by Pack Cementation Coating

Titanium possesses a unique ability to bind with bone and living tissue, making it an ideal material for orthopedic implants such as knee and hip replacements. Because of the strength to weight ratio, hermeticity, biocompatibility and light weight makes titanium and its alloy the best choice for implant. The main goal focused on studying the influence of surface coating of some titanium base alloys by Nano (ZrO2&Y2O3) to the surface roughness of implant alloys. Preparation of samples was accomplished by using powder technology technique, in which the raw materials was pure titanium, 10%cobalt,50% nickel, and 30% tantalum powders. The samples were cleaned by ultrasonic device the surface pre- treated by chemical etching, then deposition of nano (ZrO2 with Y2O3) accomplished by pack cementation process. After samples characterization by (X-ray diffraction, hardness test, porosity percentage and Surface roughness). The result showed that diffraction patterns gained for the samples were the phases developed as a result of sintering and after deposition, There are likely no presents of pure metals that prove the time and temperature of sintering utilized in this work results in full sintering reactions, the XRD patterns of samples after (ZrO2,Y2O3) deposition by pack cementation process. It is obvious that Amorphous behavior was observed in the XRD after deposition nearly at 2θ (15.799) for all samples. It is evident that the porosity percent of the samples after (ZrO2, Y2O3) deposition was largely decreases due to the pack cementation process. There was considerable increasing in hardness value, finally the roughness values obtained from the AFM it was found that there are large changes in the roughness value of samples after coating due to full the surface by Nano ceramic material deposition.

Microstructures and Oxidation Behaviors of Silicide Coated Nb Alloys by Halide Activated Pack Cementation Process

In this study, we tried to improve the oxidation resistance of Nb-12Si (wt%) alloys at 1200 °C or higher through pack cementation coatings. Nb-12Si (wt%) alloys were prepared by arc-melting under Ar atmosphere. When the alloys were coated using pack powder mixtures composed of Si, Al2O3 and NaF, two silicide layers composed of NbSi2 and Nb5Si3 phases were successfully produced on the substrate. The Si-pack coatings were performed with various heat treatment temperatures and time conditions. The microstructures and thickness changes of the coating layers were analyzed to determine the growth behaviors of the coating layer. The growth constant of 8.4 10–9 cm2/sec was obtained with a diffusion growth mode. In addition, in order to examine the resistance of the Si-pack coated alloys, isothermal static oxidation tests were performed at 1200 °C and higher temperatures. As a result, the oxidation resistance of the alloys was determined by protecting the surface of the alloys with silicide oxide layers formed by the silicide coatings. The uncoated specimens exhibited an abnormal weight increase due to the formation of Nb oxide. The coated specimen showed excellent oxidation resistance at 1200 °C for up to 12 hrs, while the previous reports on the same alloy verified oxidation resistance only up to 1100 °C. It appears that the excellent oxidation resistance is closely related to the NbSi2 coating layer thickness. The oxidation behaviors of the coating layers after the oxidation tests were discussed in terms of microstructural and phase analyses.

Evolution of the Microstructure and Properties of Pre-Boronized Coatings During Pack-Cementation Chromizing

The effect of chromizing time on the microstructure and properties of B–Cr duplex-alloyed coating prepared by a two-step pack-cementation process was investigated. The phases, microstructure, and element distribution of three coatings obtained were characterized by X-ray diffraction (XRD), secondary electron imaging (SEI), backscattering electron imaging (BSEI), and energy dispersive spectroscopy (EDS), respectively. The results show that as the chromizing time increases, the net-like Fe2B and rod-like CrFeB phases in the coating gradually disappear, and finally completely transform into the block-like Cr2B and CrxCy (Cr7C3 and Cr23C6) phases. The growth kinetics analysis shows that interface reaction dominates the coating growth during the early stage of chromizing, while atomic diffusion gradually controls the coating growth at the later stage. The evolution mechanism of the B-Cr duplex-alloyed coating was also discussed.

Microstructures and Wear Resistance of Boron-Chromium Duplex-Alloyed Coatings Prepared by a Two-Step Pack Cementation Process

In this study, a two-step pack cementation process (preboronizing and then chromizing) was employed to prepare the B-Cr duplex-alloyed coating on the steel. After the first step of preboronizing (PB sample), box-type furnace chromizing (BC-1 sample) and induction heating chromizing (BC-2 sample) were carried out, respectively. The phases and microstructure of the coatings were characterized by X-ray diffraction (XRD), backscattering electron imaging (BSEI), and energy dispersive spectroscopy (EDS). The results reveal that the heating mode of the second step of chromizing has a significant effect on the phase composition and microstructure of the B-Cr coating. The efficiency of induction heating is higher than that of the box furnace heating, resulting in a thicker, denser, flatter surface, and B-Cr coating with fully reacted B and Cr elements. The wear and corrosion resistance of the steel is found to be significantly improved by the formation of effective B-Cr coating. The formation mechanisms and properties of the two duplex-alloyed coatings are investigated and discussed.