Abstract High chromium cast iron (HCCI) with levels around 26% Cr - 2.9% C according to ASTM A 532 IIIA is widely used in systems where high abrasive wear resistance is required. To evaluate the niobium influence, HCCI with 0.5% Nb and 1% Nb additions were melted, besides one without niobium addition of for comparison. For characterization, X-ray diffractometry, scanning electron microscopy (SEM), Vickers microhardness tests, Rockwell C hardness, carbide quantifications, quantification of the retained austenite by Mössbauer spectroscopy, and rubber wheel abrasion test according to procedure A of ASTM G-65 were performed. The results indicated a reduction in the average size, average perimeter, and carbides volumetric fraction (CVF) due to the addition of niobium, also changing the microstructure of the HCCI from eutectic to hypoeutectic. In some regions, NbC0.75 carbides formed a coating around M7C3 carbides. The 0.5% Nb alloy showed the best performance in the rubber wheel abrasive wear test, with a 37% average volume loss reduction as compared to the sample without niobium addition with a 130N load and 34% with a 45N load. The 0.5% Nb alloy also had the highest content of retained austenite among the investigated alloys.

Abstract High Chromium Cast Iron (HCCI) is mostly utilised in environments under severe abrasion and corrosion wear conditions, and research on this material with added niobium obtained positive results regarding wear resistance. The casting process has surface finish and dimensional accuracy limitations compared to machining processes. There are too few studies about HCCI machinability and no one about HCCI with niobium additions. HCCI machinability studies may allow new applications for this material when excellent surface finish and high dimensional accuracy are required. This study analyses the influence of 0.5% Nb addition on the microstructure and machinability of a HCCI alloy with 25.6% Cr and 3.2% C. The samples were heat treated and subsequently machined in dry cutting conditions. Annealing was used to facilitate the pre-machining of the samples, which were later quenched and tempered. Microstructure and hardness were analysed at each stage of the heat treatment. The material was machined after tempered using polycrystalline cubic boron nitride (pcBN) tools. The alloys solidified in the hypereutectic condition. The addition of niobium reduced the hardness and carbide volumetric fraction, increased the service life of the cutting tools in all tests, provided better surface finishing and modified the wear mechanisms.

ABSTRACT High chromium cast iron (HCCI) is usually employed in equipment that experience high abrasive wear and therefore requires high resistance. Niobium could be added to these alloys to improve their resistance to wear. This study consisted in addressing the influence of 0.5% and 1.0% of niobium on the microstructure of a 26% Cr and 2.8% C HCCI alloy. Standard samples – without niobium – and samples with 0.5% and 1.0% Nb were melted, cut and then machined into adequate dimensions for tests. Two groups of samples – with and without heat treatment – were analyzed through X-ray Diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), Vickers and Rockwell-C hardness. Carbides Volume Fraction (CVF) was quantified in the heat-treated samples. The majority of NbC carbides were observed to be thin and presented a hook shaped morphology. In addition, it was noted a precipitation of Nb-rich layers around the M7C3 carbides, which could act as a higher hardness coating. There was significant reduction in carbide volume fraction, from an initial 33.3% to 28.1% for the 0.5 % Nb alloy, and further reduction to 24.9% for the 1.0% Nb alloy, it was also noted an alteration on the quasi-eutectic microstructure to a hypoeutectic microstructure. The NbC carbides prevented hardness reduction as a result of lowering the CVF in heat-treated alloys; however, the alloys without heat treatment experienced reductions in hardness.

Resumo Objetivo Identificar biomarcadores de resposta à quimioterapia neoadjuvante em câncer luminal de mama. Métodos Estudo transversal em que foram incluídas todas as pacientes com câncer luminal de mama em estádio inicial ou localmente avançado que foram submetidas a quimioterapia neoadjuvante nos anos de 2013 e 2014. Dados demográficos, clínicos e patológicos foram obtidos de prontuários médicos. As expressões de receptor de estrogênio (RE), de receptor de progesterona (RP), e de Ki67 foram avaliadas por imuno-histoquímica (IHQ). A expressão do receptor tipo 2 do fator de crescimento epidérmico humano (human epidermal growth factor receptor 2, HER2) foi avaliada por IHQ e hibridização in situ por imunofluorescência (HISI). Análises de regressão logística e de curva de característica de operação do receptor (COR) foram usadas para investigar fatores preditivos independentes de resposta clínica e patológica. Resultados De 298 pacientes identificadas, 115 foram incluídas na análise. Resposta clínica completa (RCc) foi observada em 43.4% das pacientes (49/113), e resposta patológica completa (RPc), em 7.1% (8/115). Os fatores preditivos independentes de RCc foram status menopausal (p < 0.001), baixa expressão de RP (≤ 50% versus > 50%; p = 0.048), e expressão de Ki67 ≥ 14% (versus < 14%; p = 0.01). Pacientes com RCc apresentaram maior probabilidade de serem submetidas a cirurgia conservadora da mama (34.7% versus 7.8%; p < 0.001). Aumento no ponto de corte para expressão de Ki67 foi associado a aumento da especificidade e redução da sensibilidade na identificação de pacientes com RCc. Conclusão Status premenopausal, baixa expressão de RP e maior expressão de Ki67 estiveram associados a maior taxa de RCc à quimioterapia neoadjuvante no câncer luminal de mama.

Abstract Objective To identify the biomarkers of response to neoadjuvant chemotherapy in early luminal breast cancer. Methods A cross-sectional study that included all patients with early or locallyadvanced luminal breast cancer submitted to neoadjuvant chemotherapy between 2013 and 2014. Demographic, clinic and pathologic data were retrieved from patient records. The expressions of the estrogen receptor (ER), the progesterone receptor (PR), and Ki67 were analyzed by immunohistochemistry (IHC). The status of the human epidermal growth factor receptor 2 (HER2) was evaluated by IHC and fluorescent in situ hybridization (FISH). Independent predictors of clinic and pathologic response were evaluated by stepwise logistic regression models and receiver operating characteristic (ROC) curve analysis. Results Out of 298 patients identified, 115 were included in the analysis. Clinical complete response (cCR) was observed in 43.4% of the patients (49/113), and pathologic complete response (pCR) was observed in 7.1% (8/115) of the patients. The independent predictors of cCR were premenopausal status (p < 0.001), low PR expression (≤ 50% versus > 50%; p = 0.048), and Ki67 expression ≥ 14% (versus < 14%; p = 0.01). Patients with cCR were more commonly submitted to breast conserving surgery (34.7% versus 7.8%; p < 0.001). Increasing cut-off points for Ki67 expression were associated with an increase in specificity and a decrease in sensitivity to identify patients with cCR. Conclusion Premenopausal status, lower PR expression and higher Ki67 expression were associated with a higher rate of cCR to neoadjuvant chemotherapy in luminal breast cancer.

Surface integrity has significant effect on service performance of a component. The surface integrity of workpieces submitted to grinding process depends on the conditions of cooling produced by cutting fluids, which are used to avoid microstructural damage in the process. However, cutting fluids are harmful to the environment and human health, and appear as a crucial element to the optimization of the manufacturing process. In this scenario, biodegradable cutting fluids, such as formulations based on vegetable oils, appear as promising possibility to a cleaner production in grinding process. This study analyzed the surface integrity of AISI 4340 steel, quenched and tempered, in the external cylindrical plunge grinding process with the use of six different formulations of biodegradable cutting fluids (with oils of soybeans, corn, and mineral oil, pure and with additives). The performance of the application of cutting fluids was evaluated by characterizing the microstructure by Scanning Electron Microscopy - SEM and microhardness and roughness measurements. The results showed that the surface integrity of the components was not significantly damaged, which proves the efficiency of biodegradable cutting fluids and feasibility of its use in grinding process.

Over the years, grinding has been considered one of the most important manufacturing processes. Grinding is a high precision process, and the loss of a single workpiece in this stage of the production is unacceptable, for the value added to the material is very high due to many processes it has already undergone prior to grinding. This study aims to contribute toward the development of an experimental methodology whereby the pressure and speed of the air layer produced by the high rotation of the grinding wheel is evaluated with and without baffles, i.e., in an optimized grinding operation and in a traditional one. Tests were also carried out with steel samples to check the difference in grinding wheel wear with and without the use of baffles.

The application of cutting fluid in a deep grinding process is becoming more and more important, mainly where the cutting fluids are used as an "external" agent to the grinding conditions. The role of the fluid in grinding operations is in refrigeration of the workpiece, removal of the shavings, lubrication of the grinding zone, and refrigeration and cleaning of the wheel. The efficiency of a cutting fluid will depend mainly of the type of fluid that will be used. In this work, the influences of the type of cutting fluid used in a deep grinding process of the steel VC131 using CBN grinding wheel are analyzed. Three different types of cutting fluids were used: a vegetable emulsion, a synthetic solution and a integral oil. The variables analyzed during and after the grinding process were the grinding force, the superficial roughness, the acoustic emission (EA), the temperature of the piece and the G ratio (relationship between the volume of material removed from the piece and the volume worn off the grinding wheel). The integral oil showed the best performance relative to the following output variables: EA, cutting force and G ratio. The vegetal emulsion was the fluid that best dissipated heat from the cutting region.

Nesse trabalho, procurou-se estudar os mecanismos de desgaste de diversas geometrias de ferramentas cerâmicas (Al2O3 + SiCw e Al2O3 + TiC) e ferramentas de PCBN. Para isto foram realizados ensaios de torneamento com alta velocidade de corte em uma superliga à base de níquel (Waspaloy) com dureza de aproximadamente 40 HRC sob condição de corte a seco. As superligas são conhecidas como materiais de difícil usinabilidade devido à alta dureza, alta resistência mecânica em alta temperatura, afinidade para reagir com materiais da ferramenta e baixa condutividade térmica. Os resultados mostraram que o material da ferramenta e a geometria influenciaram o comportamento dos mecanismos de desgaste. De uma maneira geral, o tipo de desgaste dominante foi o de entalhe e os mecanismos foram abrasão, attrition (aderência com arrastamento) e provável difusão na maioria das ferramentas utilizadas.

The purpose of this work is to study the wear mechanisms in several geometries of ceramic tools (Al2O3 + SiCw and Al2O3 + TiC) and PCBN tools. Several high speed turning experiments were accomplished in nickel-base superalloy (Waspaloy) with hardness of approximately 40 HRC under dry cutting condition. The nickel based superalloys are known as difficult to cut materials due to their high hardness, high mechanical straight at high temperature, chemical affinity to tool materials and lower thermal conductivity. The results showed that the material of the tool and geometry influence the behavior of wear mechanisms. In general, the dominant type of wear was notching and the mechanisms were abrasion, attrition and probable diffusion in most of the used tools.

This paper presents a review of researches on CBN (cubic boron nitride) grinding wheels with the purpose of identifying the state of art in abrasive machining and serving as the basis for future researches and laboratory tests. The scientific studies investigated here report on interesting results involving grinding, published by Brazilian and foreign authors. The methods and the results are presented and discussed. In addition, a grinding setup is presented which provides more reliable experimental results about the surface integrity of fragile materials. This setup was obtained for grinding tests in several grinding conditions during the wheel service life, using alumina and vitrified and resin bond CBN grinding wheels. Results of cutting force, surface roughness and G ratio are also presented and discussed. They confirm the excellent machining capacity of the CBN wheel, with stable behavior in cutting force and roughness results during the tests. The G ratio values are in agreement with the results found by other researchers.