IMPROVING THE PERFORMANCE OF MINERAL CERAMIC BLADE CUTTING TOOLS

The article considers the possibility of improving the performance of mineral-ceramic cutting plates by removing most of the defects on their working surface due to the formation of functional surface layers by ion-vacuum treatment. A model of a surface-hardened layer for VOK-60 type ceramics is proposed. Based on the configuration model of the substance, chemical elements are selected for modifying the surface layer of ceramics. The results of laboratory and production tests that showed an increase in the performance of ceramic plates after implantation by at least two times are presented.

Quench Process and Steel Chemistry Optimization to Prevent Quench Cracking during Hardening of Splined Semi – Axles

In the paper the hardening process of splined semi-axles is discussed and physics of preventing the quench crack formation during intensive quenching (IQ) is explained. It is shown that during IQ process at the splined cylindrical surface very high compressive current band residual stresses are formed which prevent the possibility of quench crack formation on splines. It is enough to optimize the stress distribution through the section of semi-axle and perform IQ process in order to prevent quench cracks formation in splines. It is achieved via optimizing depth of surface hardened layer. In this case the depth of surface hardened layer for cylinders and for cylinders with splines are the same. There is no need to create a special thin shell on splines or perform carburization to create such shell. Due to larger martensite specific volume, it results in surface compressive residual stress formation. Absence of martensite phase at the core eliminates core swelling that could be a reason in tensile surface stresses. The idea is supported by FEM calculations and testing of real semi-axles in industrial condition. The new idea simplifies cardinally technological process and makes it less costly.

Ultrasonic Testing for the Hardened Layer Depth of Induction Quenched 20CrMo Axle

The interface between the surface hardened layer and the base layer would produce while the 20CrMo axis is treated with high frequency induction quenching method; therefore, the hardened case depth can be measured by high frequency ultrasonic wave based on the echo technique. The test results compared with those from the metallographic method show good qualitative agreements.

Young's Modulus Profile in Kolsterized AISI 316L Steel

AISI 316L steel, subjected to a low temperature carburizing treatment (kolstering), has been examined by Mechanical Spectroscopy (MS) and nanoindentation to determine the Youngs modulus of the surface hardened layer (S phase). MS results showed that the average value of elastic modulus of S phase is 202 GPa, a little higher than that of the untreated material.Nanoindentation tests, carried out with loads of 5, 15 and 30 mN, evidence a modulus profile vs depth: E is ~ 400 GPa at a distance from the surface of ~ 110 nm, then decreases to reach the value of the steel substrate (190 GPa) at 33 μm.These results, together with X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) measurements of carbon concentration profile, can be explained by considering the presence of a very thin surface layer, different from S phase and consisting of a mixed structure of Diamond-like carbon (DLC) and tetrahedral carbon (taC).Furthermore, the same experiments have been carried out also after heat treatments at 450 °C to correlate the modulus change to the decomposition of the metastable S phase leading to the formation of (Cr,Mo)C and Cr23C6 carbides in a Cr-depleted austenitic matrix.