Structure and Properties of Heat-Resistant Alloys NiAl–Cr–Co–X (X = La, Mo, Zr, Ta, Re) and Fabrication of Powders for Additive Manufacturing

The NiAl–Cr–Co–X alloys were produced by centrifugal self-propagating high-temperature synthesis (SHS) casting. The effects of dopants X = La, Mo, Zr, Ta, and Re on combustion, as well as the phase composition, structure, and properties of the resulting cast alloys, have been studied. The greatest improvement in overall properties was achieved when the alloys were co-doped with 15% Mo and 1.5% Re. By forming a ductile matrix, molybdenum enhanced strength characteristics up to the values σucs = 1604 ± 80 MPa, σys = 1520 ± 80 MPa, and εpd = 0.79%, while annealing at T = 1250 ℃ and t = 180 min improved strength characteristics to the following level: σucs = 1800 ± 80 MPa, σys = 1670 ± 80 MPa, and εpd = 1.58%. Rhenium modified the structure of the alloy and further improved its properties. The mechanical properties of the NiAl, ZrNi5, Ni0.92Ta0.08, (Al,Ta)Ni3, and Al(Re,Ni)3 phases were determined by nanoindentation. The three-level hierarchical structure of the NiAl–Cr–Co+15%Mo alloy was identified. The optimal plasma treatment regime was identified, and narrow-fraction powders (fraction 8–27 µm) characterized by 95% degree of spheroidization and the content of nanosized fraction <5% were obtained.

Producing wear-resistant materials by SHS-casting with the application of centrifugal forces

The paper is devoted to the problem of producing hard, wear-resistant materials by SHS-casting using centrifugal forces. We have developed a device for centrifugal SHS casting and initial compositions of the reactive iron-base charge. A technology for producing coatings, materials and final products with a non-uniform distribution of strengthening particles over the specimen volume has been developed and tested in industrial conditions. The microstructure and phase composition of the synthesized material with a non-uniform distribution of reinforcing particles is studied. The synthesized material implements the Charpy principle: dispersed hard carbide particles are distributed in a relatively soft matrix, which ensures high wear resistance. By means of SHS casting, billets were obtained for producing a measurement instrument, namely a plug-type gauge, which successfully passed industrial tests at OJSC “VIZAS”. The tests shown that the hardness of all synthesized samples was in the range from 63 to 68 HRC and the number of measurements per 1 micron of wear on a diameter of15 mm was 2500 to 2700. Hence, the developed method made it possible to significantly increase the service life of the measuring tool: by a factor of 1.5 to 2.

Strength of SHS Aluminium Cast Iron from Dispersed Mechanical Engineering Waste

The article presents an alternative method of obtaining aluminium cast iron in the process of self-propagating high-temperature synthesis from disperse waste of machine-building enterprises. The deficiencies of the traditional methods for obtaining structural iron castings with aluminum are established. The analysis of the factors influencing the strength of the SHS aluminium cast iron, the planned experiment for obtaining the maximum strength of SHS aluminium cast iron for two input factors varying at three levels and three parallel observations were carried out. The statistical processing of experimental results is performed. The mathematical model is obtained for the dependence of operational factors on the composition of the charge of the SHS process. The significance of the regression coefficients of the equation is determined. The adequacy of the obtained equation is checked for the results of observations. The analysis of the conditions for the formation of the microstructure of aluminium cast iron in the process of SHS-casting is presented.

Research on the TiC Reinforced Steel Matrix Surface Composites Prepared by SHS Casting

In this paper, TiC reinforced steel matrix surface composites were prepared by vacuum evaporative casting infiltration process and self-propagating high-temperature synthesis. The effect of original composition, binder types and original coating density on the hardness, wear resistance and microstructure of the coating were also studied. The results showed that the Ti and C content was 80% while added 3% PVA, by pressed at 200MPa pressure leading optimal coating quality. Meanwhile the average hardness was 48HRC and the wear rate was 40%.