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A comparative study was carried out on GTAW AISI 316 welds fabricated by three different filler metals including ER-317M, ER-316 and ER-308. Filler metals were selected in a way to induce varying Molybdenum (Mo) concentrations in the weld metal, so that the effect of Mo on the microstructural, mechanical and corrosion behavior of the welds was investigated. Microstructural studies revealed that as Mo concentration increased in the weld metal, the dendritic morphology of this zone gradually was changed from cellular dendritic to columnar dendritic and a noticeable amount of austenitic phase and precipitations were formed. Mo-containing ER-316 and ER-317M welds showed appreciable amount of Mo- and Cr-rich carbides such as (Fe,Cr)23C6 which formed at the grain boundaries of δ-ferrite phase resulting in increased the hardness and strength of welded samples. The highest microhardness value of 188 HV and yield strength of 330 MPa belonged to ER-317M welds containing the highest Mo concentration. Also, corrosion resistance of the welds significantly improved by increasing Mo concentration and a minimum corrosion rate of 4.178 mm/year was accounted for ER-317M welds in which, the formation of passive film was more facilitated due to the higher concentration of Mo.

This paper reports on the mechanical properties of the dissimilar joints between AISI 316 austenitic stainless steel and St 37 low carbon steel achieved using friction stir welding technique. The welding was carried out by means of rotational speed of 800 rpm and linear speeds of 50,100,150 mm/min. EDS and XRD techniques were employed in order to determine possible phase transformations. Tensile test, shear punch test and microhardness measurements were conducted to evaluate the mechanical properties of the joints. The results of phase investigations showed that no carbide and brittle phase were detected at the joint boundary. Also, tensile test results demonstrated that failure occurred in the St 37 base metal. According to the shear punch test, the highest ultimate shear strength and yield shear strength was achieved for the sample welded at rotational speed of 800 rpm and linear speed of 150 mm/min, while this sample showed the least elongation. In addition, the highest microhardness was measured in the stir zone of austenitic stainless steel sample welded in the above mentioned welding condition, which can be attributed to the decrease in grain size caused by recrystallization process.

O fresamento do aço inoxidável austenítico é um processo importante para a produção de peças em que se deseja alta resistência mecânica e à corrosão. No entanto, a usinagem desse material representa um desafio por suas características adversas ao corte. A alta taxa de encruamento e a alta dureza relativa fazem-no resistente ao corte, podendo gerar vibrações em diferentes faixas de frequência. Uma técnica importante ao processamento de sinais de vibração é a Transformada de Wavelet que permite analisar diferentes frequências do sinal através da subdivisão em aproximações e detalhamentos. Neste trabalho analisaram-se vibrações em alta e baixa frequência geradas no fresamento frontal do aço inoxidável austenítico AISI 316 a partir de sinais de força, coletados por meio de um dinamômetro piezelétrico e processados via Transformada de Wavelet Discreta. Também se fez a investigação dos perfis de rugosidade, dos parâmetros de rugosidade média (Ra) e média parcial (Rz) e das ondulações gerados na superfície fresada. Nos ensaios, foram utilizados insertos com três raios de ponta distintos, hastes da fresa com três diferentes comprimentos em balanço e foram variadas a rotação do eixo-árvore e a profundidade de corte axial em três níveis cada, totalizando 81 combinações de parâmetros. Constatou-se que a profundidade de corte representou a maior influência na vibração. Na usinagem com rotações abaixo do valor mínimo recomendado pelo fabricante (1600 rpm), houve dificuldades na formação e remoção do cavaco. A modificação do raio de ponta influenciou mais a vibração em pequenas profundidades de corte ou em zonas próximas às condições de instabilidade. O comprimento da haste mostrou comportamentos diferentes para a vibração, podendo estar relacionado com a mudança das frequências naturais do sistema e também pode definir entrada em regime instável. Verificou-se correlação do detalhamento (D1) da força resultante (vibração em altas frequências) com o parâmetro Ra para condições de vibrações intensas (maiores amplitudes), mas em regime estável. Assim, o parâmetro D1 pode ser utilizado na detecção de vibrações chatter no processo de fresamento frontal do aço inoxidável AISI 316. The milling of austenitic stainless steel is important process for the production of part that require mechanical and corrosion resistance. However, the machining of this steel represents a challenge by its adverse features. The high hardening rate and the high relative hardness make it resistant to cutting and can generate vibrations in different frequency ranges. An important technique for the processing of vibration signals is the Wavelet Transform that allows the analysis of different signal frequencies through the subdivisions into approximations and details. In this work, high and low frequency vibration generated in end milling of AISI 316 stainless steel were analyzed from force signals collected through a piezoelectric dynamometer and processed via Wavelet Discrete Transform. Besides, the roughness profiles were investigated, as well as average (Ra) and partial mean (Rz) roughness parameters, and waviness generated on the milled surface. Three different insert nose radius, end mill tool lengths, depths of cut and spindle speeds were used in the experiments, totaling 81 combinations of parameters. It was found that depth of cut represented the greatest influence on vibration. In end milling with spindle speed below the minimum recommended by the tool manufacturer (1600 rpm) it occurred difficulties in the chip formation and removal. The modification of tool nose radius greater influenced the vibration at small depths of cut or in regions close to the stability limit. The end mill tool length showed different behaviors for the vibration, which may be related to the change of natural frequencies of the mechanical system and may also define an unstable state. The correlation of detail (D1) of the resulting force (vibration at high frequencies) with the parameter Ra for intense vibration conditions (larger amplitudes) was verified, but in stable state. Thus, D1 can be used for detecting chatter in end milling process of AISI 316 stainless steel.