Study of the mechanical and metallurgical properties of sintered steels for valve seat inserts application

Abstract

The aim of this work was to study the valve seat insert (VSI) produced with three different alloys (mainly modified from the original AISI M3/2, M2 and D2 high-speed steels) from the mechanical and metallurgical point of view. These alloys modifications were intended as an alternative to replace cobalt and lead used in the original alloy due to their high cost and toxicological effect respectively. Such alloys have been developed for internal combustion engines VSI manufacture. The VSI studied in this work was previously produced by the powder metallurgy (P/M) route. The VSI production was performed using a uniaxial hydraulic press and a belt conveyor furnace. The VSI was submitted to metallic infiltration during the sintering process using copper as filler. The studies were performed according to standardized apparent density (ASTM C 373-88), apparent hardness (ASTM E 92-82) and radial crush strength (MPIF Standard 35) tests. The VSI produced with M3/2 alloy proved to be more advantageous considering the highest values obtained in the apparent hardness and radial crush strength tests.Keywords: powder metallurgy, characterization, valve seat insert, high-speed steel. ResumoO objetivo deste trabalho foi estudar o inserto para assento de válvula (do inglês VSI -Valve Seat Insert) produzido com três ligas diferentes (modificadas principalmente das ligas originais de aço rápido AISI M3/2, M2 e D2) do ponto de vista mecânico e metalúrgico. As modificações destas ligas foram pretendidas como uma alternativa para substituir o cobalto e o chumbo usados na liga original, devido ao seu custo elevado e efeito toxicológico respectivamente. Tais ligas têm sido desenvolvidas para a manufatura de VSI utilizados em motores à combustão interna. O VSI estudado neste trabalho foi produzido pela rota da metalurgia do pó (M/P). Este processo foi realizado utilizando-se uma prensa hidráulica de compactação e um forno contínuo de esteira. Os VSI foram submetidos a infiltração metálica durante a etapa de sinterização utilizando cobre como infiltrante. Os estudos foram determinados de acordo com testes padronizados, sendo eles: densidade aparente (ASTM C 373-88), dureza aparente (ASTM E 92-82) e resistência à ruptura radial (MPIF padrão 35). Os VSI produzidos com a liga M3/2 provaram ser mais vantajosos considerando-se os valores obtidos nos ensaios de dureza aparente e resistência à ruptura radial.Palavras-chave: metalurgia do pó, caracterização, inserto de assento de válvula, aço rápido.

Caracterização De Insertos Para Assentos De Válvulas Sinterizados Obtidos Com O Aço Rápido Aisi M2 Depois De Temperados Ao Ar

“…Briefly, the results of the properties mentioned previously is shown in Table 4. In comparison with the work developed previously by Santos et al [6][7][8], only with as sintered components, the apparent density can be considered the same, 7.4 g/cm 3 . The apparent hardness values measured by Santos [7] was lower, 345 ± 21 HB, than the one obtained in the present work, 392 ± 1 HB.…”

“…The aim of this work was to air quench, double temper in different temperatures, and characterize all the sintered valve seat inserts obtained with the powders mixtures of AISI M2 high-speed steel, iron, and others additives. Santos et al [6][7][8] previously developed the studied VSI, and he has only evaluated the as sintered VSI.…”