Ultra-low-temperature process treatments could raise tool steel wear resistance through microstructural change that occurs on the material, enhancing, that way, tools and dies lifetime. To investigate the tool steel wear resistance impact, micro-abrasive wear tests were carried out and an analysis based on the Archard's law was considered, evaluating specimen mass loss by laser interferometry. Micro-hardness, X-ray diffractometry, scanning and optical microscopy and carbides quantitative evaluation were carried out aiming to material characterisation. Results demonstrated a micro-hardness improvement, ranging from 0.9–4.7% for the cryogenically treated specimens, when compared to the bulk material. This effect is related, mainly, to the retained austenite transformation and to the increase of fine secondary carbides dispersed amount in the martensitic matrixes cryogenically treated.

Low temperature plasma carburizing treatment of austenitic stainless steels is a carbon surface diffusion process for a surface hardness and corrosion and wear resistance. The process is carried out by introducing a mixture of carbon-containing gases and through the use of low temperatures the resulting cemented layer usually contains a single phase of supersaturated austenite with carbon – S-phase. For the present investigation, austenitic stainless steels AISI 316L and 304 were plasma cemented for 8 hours in the gas mixture containing 7.5% CH4 in H2, with a pressure of 500 Pa, at temperatures of 375 ºC and 450 ºC. The phases formed were determined by X-ray diffraction. The corrosion resistance was evaluated through immersion tests over time and cyclic voltammetry. The results indicate that there was no formation of compounds (carbides) in the cemented layer for both steels at any of the temperatures and there was a corrosion resistance improvement.

Superalloys are used primarily for the aerospace, automotive, and petrochemical industries. These applications require materials with high creep resistance. In this work, evaluation of creep resistance and microstructural characterization were carried out at two new nickel intermediate content alloys for application in aerospace industry and in high performance valves for automotive applications (alloys VAT 32 and VAT 36). The alloys are based on a high nickel chromium austenitic matrix with dispersion of intermetallic L1₂ and phases containing different (Nb,Ti)C carbides. Creep tests were performed at constant load, in the temperature range of 675–750 °C and stress range of 500–600 MPa. Microstructural characterization and failure analysis of fractured surfaces of crept samples were carried out with optical and scanning electron microscopy with EDS. Phases were identified by Rietveld refinement. The results showed that the superalloy VAT 32 has higher creep resistance than the VAT 36. The superior creep resistance of the alloy VAT 32 is related to its higher fraction of carbides (Nb,Ti)C and intermetallic L1₂ provided by the amount of carbon, titanium, and niobium in its chemical composition and subsequent heat treatment. During creep deformation these precipitates produce anchoring effect of grain boundaries, hindering relative slide between grains and therefore inhibiting crack formation. These volume defects act also as obstacles to dislocation slip and climb, decreasing the creep rate. Failure analysis of surface fractures of crept samples showed intergranular failure mechanism at crack origin for both alloys VAT 36 and VAT 32. Intergranular fracture involves nucleation, growth, and subsequent binding of voids. The final fractured portion showed transgranular ductile failure, with dimples of different shapes, generated by the formation and coalescence of microcavities with dissimilar shape and sizes. The occurrence of a given creep mechanism depends on the test conditions. At creep tests of VAT 32 and VAT 36, for lower stresses and higher temperature, possible dislocation climb over carbides and precipitates would prevail. For higher stresses and intermediate temperatures shear mechanisms involving stacking faults presumably occur over a wide range of experimental conditions.

Titanium alloys have a high cost of production and exhibit low resistance to abrasive wear. The objective of this work was to carry out diamond-like carbon (DLC) coating, with dissimilar thicknesses, on Ti-22Nb-6Zr titanium alloys produced by powder metallurgy, and to evaluate its microabrasive wear resistance. The samples were compacted, cold pressed, and sintered, producing substrates for coating. The DLC coatings were carried out by PECVD (plasma-enhanced chemical vapor deposition). Free sphere microabrasive wear tests were performed using alumina (Al₂O₃) abrasive suspension. The DLC-coated samples were characterized by scanning electron microscopy (SEM), Vickers microhardness, coatings adhesion tests, confocal laser microscopy, atomic force microscopy (AFM), and Raman spectroscopy. The coatings did not show peeling-off or delamination in adhesion tests. The PECVD deposition was effective, producing sp2 and sp3 mixed carbon compounds characteristic of diamond-like carbon. The coatings provided good structural quality, homogeneity in surface roughness, excellent coating-to-substrate adhesion, and good tribological performance in microabrasive wear tests. The low wear coefficients obtained in this work demonstrate the excellent potential of DLC coatings to improve the tribological behavior of biocompatible titanium alloy parts (Ti-22Nb-6Zr) produced with a low modulus of elasticity (closer to the bone) and with near net shape, given by powder metallurgy processing.

Nowadays, it is hard to imagine modern industry without the manufacturing and design software aided by computer, known as CAD/CAM, once the search for excellence in complex geometry parts, reduced time, quality assurance and interchangeability is increasing. Within this quest, the CAD/CAM platform has become a significant factor in manufacturing, especially on complex surfaces parts, mainly because of superficial quality, reliability and product competitiveness. Defined as surface within one or more non-flat surfaces or non-square, usually represented by parametric models, the freeform surfaces are very complex, requiring the control of three or more axes simultaneously, making the CAM tool indispensable. Tests were carried out by milling of aspherical cavities, on VP100 steel samples, with cemented carbide ball nose inserts with TiAlN coating. Two cutting strategies – zig-zag and spiral – and two finishing (CAM) strategies – parallel plans and Z level – were also investigated. Final Surface quality, tool productivity and tool wear were related to machining time, surface roughness (Ra, Rz, Rku and Rsk) and tool wear (VBmax). Results showed that the chosen strategy (tool path) it is the main factor to productivity.