Anode Materials for Electrospark Alloying of Aluminium-matrix Alloys

Abstract

This paper describes the optimum compositions of four aluminium matrix alloys (A, B, C, D) obtained from oxides (NiO, TiO2, ZrO2, Cr2O3) by means of aluminothermy (self-propagating high-temperature synthesis, or SHS metallurgy). These compositions were developed in order to enhance the wear resistance of coatings on steel 45 during electrospark deposition. Depending on the composition of synthesized alloys, the authors obtained different combinations of the structural components — i.e. aluminides of Ni, Zr, Cr, Ti, complex alloyed solid solution and eutectic. The above structural components of the aluminium matrix alloys were identified by means of electron microscopy and electron probe microanalysis. The authors established and substantiated how the alloy composition can impact the structure and the distribution of elements (segregation). The synthesized alloys A, B, C and D were used as anode materials to enhance the wear resistance of coatings on steel 45. Rows of gain (∑Δк·10–4, g), erosion (∑Δа·10–4, g), transport coefficient (∑Кp, %) and wear factor (∑Иls·10–4, g) were obtained. For all of the above mentioned parameters, mathematical expressions were obtained for the polynomial equations of the trend showing kinetic dependencies on the electrospark deposition time when the studied anode materials were used in the process. A test of validity was also defined to analyze the resultant polynomial lines of the Rл trend showing the kinetic dependencies ∑Δк, ∑Δа, ∑Кp, ∑Иls. High wear resistance values could be observed in all cases when the anode material D was used in the electrospark deposition process – % (wt.): 33.29 Al; 41.6 Ni; 10.27 Cr; 4.6 Zr; 7.23 Ti; 2.98 Fe. The material D showed optimum values in all the studied modes. Correspondingly, the value ∑Иls increased by 3.27 times. Lower wear resistance values were obtained for the alloy A – % (wt.): 36.52 Al; 47.65 Ni; 15.83 Ti. The wear factor ∑Иls increased by 1.85 times. At the same time, the wear factor of steel 45 without coating when it was subjected to similar wear conditions was as follows: ∑И(st.45) = 72·10–4 g.The research was carried out under financial support of the RF Ministry of Science and Higher Education within the Government Order No. FEME-2020-0010 "Physical-chemical and technological base of metallothermic metal synthesis in metal alkali melts and complex alloyed nickel aluminides via SHS metallurgy". Investigations were conducted using equipment of the common use center "Applied materials science"of the Pacific National University.