For materials with ultrafine structures apply methods of intensive deformation, in particular equal channel angular (ECA) pressing.
This method allows to achieve a high level of mechanical properties of metals and alloys, such as copper, nickel, titanium and other by forming them in nanocrystalline (NC) structure with a grain size of 100-500 nm.
For practical use of NK-materials in various industries, more research is needed technological modes of processing. In this paper we study the tribological parameters of cold extrusion process (reduction) of commercially pure titanium BT1-0 NK with a high level of properties as a promising substitute doped titanium alloys.
It is known that because of the poor anti-friction properties during deformation titanium actively adhered to the tool at the slightest occurrence of dry friction, which leads to a sharp increase in deformation forces, tool wear and reduced product quality.
Tool life in the production of metal products made of titanium alloys by one to two orders of magnitude lower than in the production of steel wire products, because the worst of the tribological conditions of the process. Therefore, rational selection of protective coatings podsmazochnyh (FOD) and lubricants (SM) for the process of cold extrusion of titanium is an urgent task.
Efficiency RFP and SM examined under direct extrusion of commercially pure titanium. Scheme of direct extrusion is most often found in the real technological process of cold bulk deformation of metals and alloys and best simulates the conditions of contact between the workpiece and the tool in the reduction, drawing and other metal forming processes.
The effectiveness of lubricants was evaluated using the procedure described in the papers, and based on the relationship of power parameters extruding and ejecting preforms tribological process conditions. Improved tribological conditions reduces frictional forces within the container, the girdle and the sizing on the tapered section of the matrix, and therefore the extrusion force P1 and P2 depending on the movement determined by strain measurement.
Tests were carried out on the machine IR 5047-50, operating in compression mode using the experimental equipment for direct extrusion, which includes a set of matrices, punches and pushers of high tool steels X12M and P6M5. The relative degree of deformation of 30%, the strain rate — 50 mm / min. Samples in the form of cylinders 5 mm in diameter and 15 mm length excised from titanium billets 19 mm in diameter and 90 mm long, obtained by the ECAP and NK-structure having a grain size of 200-400 nm and a strength of 700 MPa.
For comparison, the tribological properties of the samples from the initial coarse grind (CP) titanium with a grain size of 15-25 microns and the strength of 450 MPa.
The samples were applied FOD conventionally used in cold deformation titanium — oxalate (oxalic acid salt) and a borate (borate), followed by saponification and without it, but in the extrusion process additionally used high CM «Rosoil-shock» and «Rosoyl- Angelina «, designed CHTC AIM. Efficacy was evaluated RFP and SM to reduce deformation forces P1 and P2 ejection.
The table shows the average data for testing five samples per pixel. Analysis of these data indicates the effectiveness of both oxalate and borate in combination with CM «Rosoil-Angelina» and «Rosoil-shock». In the absence of STDs for both structural states of the titan we observed a significant increase in the forces squeezing and pushing, and the active adhesive sticking titanium tool.
It should be noted that under equal force deformation process parameters for titanium-NK were significantly lower, although its strength is 1.5 times higher fault-titanium.
This effect can be explained better adhesion FOD (as oxalate and borate) with NC-titanium. It is also possible that the observed effect is due to buckling of the workpiece, a lower yield strength at a given degree of deformation and, as a consequence, increase in the area of the container wall friction.
When deformation NK most effective use of titanium oxalate and borate in combination with the above omylivaniya CM. The decrease in extrusion force most affected by the CM «Rosoil-shock» ceteris paribus. The best results are obtained by using borate omylivaniya and CM «Rosoil-shock».
In the deformation model samples using both CM «Rosoil-Angelina» were obtained lower values of forces squeezing and pushing. However, the reduction of field blanks oxalate scale often do not withstand even a single cycle reduction. Typically, after reduction of one third of the workpiece that is in the order of 20-30 mm, sharply (three times or more) increased the extrusion force, titanium intensively adheres to the tool on the workpiece and tears appear radical metal the complete absence FOD on its surface.
These facts point to a fragile adhesive interaction FOD with NC-titanium VT1 0.
At the same time the use of the FOD borate with saponification and SM «Rosoil-shock» allowed a cold reducing of specimens of NK-titanium with a diameter of 22 mm to 11 mm in six cycles with a relative degree of deformation per cycle to 20% at double FOD application. In the process of reducing mechanical damage of samples, as well as gaps and discontinuities FOD on the sample surface was observed.
1. The research of tribological conditions direct extrusion NK-1 titanium BT -0 on model samples in the degree of deformation of 30% and on natural patterns in sequential multicyclic deformation at a deformation per cycle to 20%.
2. It was found that the studied combination of protective podsmazochnyh coatings and lubricants the best tribological characteristics of borate has a saponification and «Rosoil-shock». This combination is recommended for use in the process of cold extrusion NC titanium BT1-0 relative degree of deformation of up to 30% per cycle of deformation.
3. With the use of this combination of RFP and SM designed CHTC AIM, conducted cold reducing NK-1 titanium BT -0 six cycles total reduction of 75% and obtained bezdefektivnye samples, the strength of which is close to the strength of the alloy titanium alloys.