The article studied the effect of annealing on the structure and properties of zirconium dioxide coatings obtained by detonation spraying. Detonation spraying was realized on a computerized detonation spraying complex of the new generation CCDS2000. Determined that coatings made of zirconium dioxide are characterized by high adhesive strength of adherence to the substrate. Thermal annealing of coated samples was performed at temperatures of 900-1200◦ C. It was determined that the microhardness of zirconium dioxide coatings increases by 10-25% depending on the annealing temperature after annealing. The results of nanoindentation showed that the nanohardness of the coatings after annealing at 1000◦ C increases by 50%. It was determined that after annealing at 1000◦ C, the elastic modulus of the coatings increases, which indicates a decrease in plasticity and an increase in the strength of the coatings. X-ray diffraction analysis showed that the phase composition of coatings before and after annealing consists of t-ZrO2. After annealing occurs there is an increase in the degree of t-ZrO2 tetragonality. Electron microscopic analysis showed that an increase in the number and size of micro-continuity in the form of thin layers after annealing. Determined that increase the hardness of zirconium dioxide after annealing at 900-1200◦ C is associated with a higher degree of tetragonality t-ZrO2 phase.
The optimal electrolyte composition for electrolyte-plasma surface hardening of 40XH steel, which does not lead to the surface layer to erosion, oxidation and decarburization are determined in this work. It is shown that after electrolytic-plasma surface hardening a modified layer with a thickness of 1–1.2 mm is formed with high hardness and wear resistance which consisting of a hardened layer of fine-grained martensite, an intermediate layer of perlite and martensite.
We investigated 18CrNi3MoA-SH steel, hardened by electrolyte-plasma processing method. Scanning analysis of transient surface demonstrated that in the course of details’ electrolyte-plasma heating chemical surface modification takes place along with tempering. Unit value of micro hardness on the crosscut is estimated. Micro hardness twofold increase concerning initial condition testifies to material hardness after electrolyte-plasma processing. This method advantages are minor energy expenditure in the time of tempering high speeds, possibility of local surface processing especially of large size details with complicated shape. 18CrNi3MoA-SH steel hardening by electrolyte-plasma method is performed on semi-industrial installation constructed at D.Serikbayev EKSTU in collaboration with «TehnoAnalyt» Ltd., Ust-Kamenogorsk. The detail heating temperature is 930 - 9400С, overall time of processing is approximately 5 minutes, hardening is produced at 860 - 8700C then cooled in electrolyte flux. Electrolyte composition is 10 %-s' Na2CO3 and C3H8O3. The metallographic analysis was realized on «NEOPHOT 21» microscope. The qualitative and quantitative phase analysis of steel structure was carried out on PANanalytical" X-Ray diffractometer involving Cu-K radiation. Microhardness determination was measured on PMT-3 device with diamond cutting point; by indentation load 1 N according to State Standard 9450-76.
This work shows the results of research of the fine and dislocation structure of the transition layer of 18CrNi3Mo low-carbon steel after the influence of electrolytic plasma. Conducted research has shown that the modified steel layer, as a result of carbonitriding, was multiphase. Quantitative estimates were made for carbonitride М23(С,N)6 in various morphological components of α-martensite and on average by material in the transition layer of nitro-cemented steel. It was established that α-phase is tempered martensite after nitrocementation. Released martensite is represented by batch, or lath and lamellar low-temperature and high-temperature martensite. Inside the tempered martensitic crystals, lamellar cementite precipitates are simultaneously present, and residual austenite is found along the boundaries of the martensitic rails and plates of low-temperature martensite. It was determined that inside the crystals of all morphological components of α-martensite there are particles of carbonitride М23(С,N)6.
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