Análise do processo de torneamento da superliga Vat 32® com ferramentas de corte experimentais e comerciais
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2019-03-21
Autores
Kondo, Marcel Yuzo [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A superliga de níquel VAT 32® foi desenvolvida como um substituto da liga UNS N07751 (Inconel 151) na fabricação de válvulas automotivas para motores de combustão interna de alto desempenho. A formação de carbonetos de nióbio confere a esta liga elevada resistência ao desgaste, desejada na aplicação em válvulas automotivas, criando-se, porém, uma maior dificuldade na usinagem deste material. Este trabalho estudou o torneamento da liga VAT 32® com quatro tipos de ferramentas de corte. São elas insertos de metal duro com diferentes revestimentos, Ti(C,N) + Al2O3 pelo processo de deposição química de vapor (chemical vapor deposition – CVD), e revestimento de Ti-Al-Si-N pelo processo de deposição física de vapor (physical vapor deposition – PVD), pastilhas de nitreto cúbico de boro (cBN) e pastilhas experimentais de Al2O3 + MgO. Através do método de Taguchi de planejamento experimental, foram obtidas as combinações e os efeitos principais dos parâmetros velocidade de corte, avanço da ferramenta, profundidade de usinagem e tipo de lubrificação (seco ou em abundância) para otimizar cada uma das variáveis respostas, sendo elas potência de usinagem, desgaste das ferramentas, qualidade superficial das peças usinadas, e os sinais de emissão acústica e vibração do processo. Foram obtidos também, através da análise da razão sinal-ruído (S/N) de Taguchi, a composição dos parâmetros de corte em que o processo apresentou menor variabilidade das características de qualidade, o chamado processo robusto. Com a utilização da análise relacional cinza (GRA), método de otimização multiobjetivo, selecionou-se uma condição para os ensaios de vida das diferentes ferramentas estudadas. Os tipos de desgaste e tipos de cavaco também foram observados. Nos ensaios de vida, onde cada um dos tipos de ferramenta trabalhou na sua condição otimizada, o melhor desempenho em relação ao comprimento usinado total até o fim de vida foi da ferramenta de metal duro CVD. Porém, quando analisada a rugosidade das peça usinada, o destaque é dado a ferramenta de PVD, pois seu comprimento total de usinagem é pouco inferior aos obtidos pela ferramenta CVD mas os valores de rugosidade obtidos são muito inferiores, cerca de pelo menos 3 vezes menor.
VAT 32® is a nickel based super alloy developed to substitute UNS N07751 alloy in production of automotive valves for high performance internal combustion engines. The formation of niobium carbides gives to this alloy a high resistance to wear, desired in the application in automotive valves, creating however, a greater difficulty in the machining of this material. This thesis aimed the study of VAT 32® turning with four different cutting tools. The tested tools were Ti(C,N)+Al2O3 coated by chemical vapor deposition (CVD) carbide inserts, Ti-Al-Si-N coated by physical vapor deposition (PVD) carbide inserts, cubic boron nitrite (cBN) inserts and experimental Al2O3+MgO ceramic inserts. Optimal combination of the cutting parameters and main effects of the factors speed of cutting, tool feed, depth of cutting and lubrication condition (dry and abundant) in turning of VAT 32® were found using Taguchi’s method as a design of experiment (DOE). The analyzed response variables were machining power, tool wear, surface quality of the machined pieces, chips format and acoustic emission and vibration signals of the process. It was also obtained in this work the robust process with the analysis of signal to noise ratio (S/N) where cutting parameters for smaller process variability were found. Finally, the multi-objective optimization method called Grey Relational Analysis (GRA) was used to find optimal cutting conditions for each tested tools. These optimal conditions were used in a tool life test. In the life tests, where each type of tool worked in its optimized condition, the best performance in relation to the total machined length till the end of life was of obtained by the CVD carbide tool. However, when the roughness of the machined part was analyzed, the highlight is the PVD tool, because its total machining length is slightly lower than those obtained by the CVD tool, but the obtained roughness values are much lower, at least 3 times lower.
VAT 32® is a nickel based super alloy developed to substitute UNS N07751 alloy in production of automotive valves for high performance internal combustion engines. The formation of niobium carbides gives to this alloy a high resistance to wear, desired in the application in automotive valves, creating however, a greater difficulty in the machining of this material. This thesis aimed the study of VAT 32® turning with four different cutting tools. The tested tools were Ti(C,N)+Al2O3 coated by chemical vapor deposition (CVD) carbide inserts, Ti-Al-Si-N coated by physical vapor deposition (PVD) carbide inserts, cubic boron nitrite (cBN) inserts and experimental Al2O3+MgO ceramic inserts. Optimal combination of the cutting parameters and main effects of the factors speed of cutting, tool feed, depth of cutting and lubrication condition (dry and abundant) in turning of VAT 32® were found using Taguchi’s method as a design of experiment (DOE). The analyzed response variables were machining power, tool wear, surface quality of the machined pieces, chips format and acoustic emission and vibration signals of the process. It was also obtained in this work the robust process with the analysis of signal to noise ratio (S/N) where cutting parameters for smaller process variability were found. Finally, the multi-objective optimization method called Grey Relational Analysis (GRA) was used to find optimal cutting conditions for each tested tools. These optimal conditions were used in a tool life test. In the life tests, where each type of tool worked in its optimized condition, the best performance in relation to the total machined length till the end of life was of obtained by the CVD carbide tool. However, when the roughness of the machined part was analyzed, the highlight is the PVD tool, because its total machining length is slightly lower than those obtained by the CVD tool, but the obtained roughness values are much lower, at least 3 times lower.
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Palavras-chave
Metal duro PVD, Metal duro CVD, cBN, Potência de usinagem, Ferramenta cerâmica, Método de Grey Taguchi, Superligas, Ligas de níquel, Ligas resistentes ao calor, Ferramentas de corte, PVD carbide tool, CVD carbide tool, Cutting power, Ceramic tool, Superalloy, Grey-Taguchi method